The possible role of mRNA expression changes of GH/IGF-1/insulin axis components in subcutaneous adipose tissue in metabolic disturbances of patients with acromegaly.

We explored the effect of chronically elevated circulating levels of growth hormone (GH)/insulin-like-growth-factor-1 (IGF-1) on mRNA expression of GH/IGF-1/insulin axis components and p85alpha subunit of phosphoinositide-3-kinase (p85alpha) in subcutaneous adipose tissue (SCAT) of patients with active acromegaly and compared these findings with healthy control subjects in order to find its possible relationships with insulin resistance and body composition changes. Acromegaly group had significantly decreased percentage of truncal and whole body fat and increased homeostasis model assessment-insulin resistance (HOMA-IR). In SCAT, patients with acromegaly had significantly increased IGF-1 and IGF-binding protein-3 (IGFBP-3) expression that both positively correlated with serum GH. P85alpha expression in SCAT did not differ from control group. IGF-1 and IGFBP-3 expression in SCAT were not independently associated with percentage of truncal and whole body fat or with HOMA-IR while IGFBP-3 expression in SCAT was an independent predictor of insulin receptor as well as of p85alpha expression in SCAT. Our data suggest that GH overproduction in acromegaly group increases IGF-1 and IGFBP-3 expression in SCAT while it does not affect SCAT p85alpha expression. Increased IGF-1 or IGFBP-3 in SCAT of acromegaly group do not appear to contribute to systemic differences in insulin sensitivity but may have local regulatory effects in SCAT of patients with acromegaly.

Three months of regular aerobic exercise in patients with obesity improve systemic subclinical inflammation without major influence on blood pressure and endocrine production of subcutaneous fat.

The aim of our study was to explore the effects of regular aerobic exercise on anthropometric, biochemical and hormonal parameters and mRNA expression of selected factors involved in metabolic regulations in subcutaneous adipose tissue of patients with obesity. Fifteen obese women with arterial hypertension underwent a three-month exercise program consisting of 30 min of aerobic exercise 3 times a week. Fifteen healthy lean women with no intervention served as a control group. Obese group underwent anthropometric measurements, blood sampling, subcutaneous adipose tissue (SCAT) biopsy and 24-h blood pressure monitoring at baseline and after three months of exercise, while control group was examined only once. At baseline, obese group had increased SCAT expression of proinflammatory cytokines and adipokines relative to control group. Three months of regular exercise improved anthropometric parameters, decreased CRP, blood glucose and HOMA-IR, while having no significant effect on lipid profile and blood pressure. Gene expressions in SCAT were not affected by physical activity with the exception of increased aquaporin-3 mRNA expression. We conclude that three months of regular exercise decrease systemic subclinical inflammation with only minor influence on the blood pressure and the endocrine function of subcutaneous fat.

Serum preadipocyte factor-1 concentrations in females with obesity and type 2 diabetes mellitus: the influence of very low calorie diet, acute hyperinsulinemia, and fenofibrate treatment.

Appropriate differentiation capacity of adipose tissue significantly affects its ability to store lipids and to protect nonadipose tissues against lipid spillover and development of insulin resistance. Preadipocyte factor-1 (Pref-1) is an important negative regulator of preadipocyte differentiation. The aim of our study was to explore the changes in circulating Pref-1 concentrations in female subjects with obesity (OB) (n=19), females with obesity and type 2 diabetes mellitus (T2DM) (n=22), and sex- and age-matched healthy control subjects (C) (n=22), and to study its modulation by very low calorie diet (VLCD), acute hyperinsulinemia during isoglycemic-hyperinsulinemic clamp, and 3 months' treatment with PPAR-α agonist fenofibrate. At baseline, serum Pref-1 concentrations were significantly higher in patients with T2DM compared to control group, while only nonsignificant trend towards higher levels was observed in OB group. 3 weeks of VLCD decreased Pref-1 levels in both OB and T2DM group, whereas 3 months of fenofibrate treatment had no significant effect. Hyperinsulinemia during the clamp significantly suppressed Pref-1 levels in both C and T2DM subjects and this suppression was unaffected by fenofibrate treatment. In a combined population of all groups, circulating Pref-1 levels correlated positively with insulin, leptin and glucose levels and HOMA (homeostasis model assessment) index. We conclude that elevated Pref-1 concentrations in T2DM subjects may contribute to impaired adipose tissue differentiation capacity associated with insulin resistance in obese patients with T2DM. The decrease of Pref-1 levels after VLCD may be involved in the improvement of metabolic status and the amelioration of insulin resistance in T2DM patients.

Liver, but not adipose tissue PEDF gene expression is associated with insulin resistance.

OBJECTIVE: Recent studies linked circulating pigment epithelium-derived factor (PEDF) to obesity-associated insulin resistance, but the main source of circulating PEDF is unknown. We aimed to investigate liver and adipose tissue PEDF gene expression in association with obesity and insulin resistance. DESIGN, SUBJECTS AND METHODS: Three (two cross-sectional and one longitudinal) independent cohorts have been studied, for adipose tissue (n=80 and n=30) and liver gene expression (n=32 and n=14). Effects of high glucose and cytokines on HepG2 cell line were also investigated. PEDF gene expression and circulating PEDF were analyzed using real-time PCR and ELISA, respectively. RESULTS: In a first cohort of subjects, PEDF relative gene expression was higher in subcutaneous (SC) than in omental (OM) adipose tissue (P<0.0001) being also higher in mature adipocytes compared with stromo-vascular cells (P<0.0001). However, OM PEDF relative gene expression was decreased in morbidly obese subjects (P=0.01). Both OM PEDF and OM PEDF receptor (PEDFR) correlated positively with lipogenic and lipolytic genes, and with genes implicated in the lipid vacuole formation. Circulating PEDF levels were not associated with fat PEDF gene expression. In the second cohort, SC PEDF was decreased in subjects with type 2 diabetes and did not change significantly after weight loss. We next explored circulating PEDF in association with markers of liver-related insulin resistance injury (alanine aminotransferase, r=0.59, P=0.001). Interestingly, liver PEDF gene expression increased with obesity and insulin resistance in men, being significantly associated with fasting glucose and glycated hemoglobin in two independent cohorts. In fact, high glucose led to increased PEDF in HepG2 cells, while inflammatory stimuli present in the adipose tissue environment downregulated PEDF. CONCLUSION: Liver, but not adipose tissue, might be the source of increased circulating PEDF linked to insulin resistance.

Serum concentrations and tissue expression of components of insulin-like growth factor-axis in females with type 2 diabetes mellitus and obesity: the influence of very-low-calorie diet.

We explored serum concentrations and mRNA expression of insulin-like-growth factor-1 (IGF-1) axis components in subcutaneous adipose tissue (SCAT) and peripheral monocytes (PM) of 18 healthy females, 11 obese non-diabetic females (OB) and 13 obese women with type 2 diabetes (T2DM) examined at baseline and after very-low-calorie diet (VLCD). T2DM women had decreased expression of IGF-1, IGF-1 receptor (IGF-1R), IGFBP-2 (IGF binding protein-2) and IGFBP-3 in SCAT and increased expression of IGF-1R in PM compared to control group. IGF-1R and IGFBP-3 mRNA expression in SCAT of OB was comparable to control group. In T2DM women VLCD increased serum levels and SCAT expression of IGFBP-2 and PM expression of IGFBP-3. We conclude that decreased IGF-1, IGF-1R and IGFBP-3 expression in SCAT and increased IGF-1R expression in PM of T2DM subjects might contribute to changes of fat differentiation capacity and to regulation of subclinical inflammation by PM, respectively. Increased SCAT and circulating IGFBP-2 and IGFBP-3 in PM might participate in metabolic improvements after VLCD.

[Insulin resistance and nitric oxide: molecular mechanisms and pathophysiological associations]. / Inzulinová rezistence a oxid dusnatý: molekulárni mechanizmy a patofyziologické souvislosti.

Subclinical inflammation that primarily arises in adipose tissue as a result of its excessive infiltration by immunocompetent cells represents one of the typical etiopathogenetic mechanisms underlying the development of insulin resistance and type 2 diabetes. Immunocompetent cells together with adipocytes are a major source of proinflammatory cytokines triggering proinflammatory cascades that in turn interfere with postreceptor insulin signalling cascade. Recent studies have suggested that inducible nitric oxide synthase plays a key role in this process. Obesity is associated with increased inducible nitric oxide synthase mRNA expression, with subsequent overproduction of nitric oxide and reactive nitrogen species leading to S-nitrosylation of proteins involved in insulin signalling cascade. These post-translational modifications decrease their activity and eventually lead to insulin resistance. Number of experimental studies demonstrated that inhibition of inducible nitric oxide synthase attenuates insulin resistance. The aim of this review is to summarize the current knowledge about the physiology and patophysiology of nitric oxide and inducible nitric oxide synthase with respect to its relationship to insulin resistance and to discuss the possibility of improvement of insulin resistance and type 2 diabetes mellitus by modulating inducible nitric oxide synthase activity.