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.

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.

The effect of very-low-calorie diet on mRNA expression of inflammation-related genes in subcutaneous adipose tissue and peripheral monocytes of obese patients with type 2 diabetes mellitus

CONTEXT

Low-grade inflammation links obesity, type 2 diabetes mellitus (T2DM), and cardiovascular diseases.

OBJECTIVE

To explore the expression profile of genes involved in inflammatory pathways in adipose tissue and peripheral monocytes (PM) of obese patients with and without T2DM at baseline and after dietary intervention.

DESIGN

Two-week intervention study with very-low-calorie diet (VLCD).

SETTING

University hospital.

PATIENTS

Twelve obese females with T2DM, 8 obese nondiabetic females (OB) and 15 healthy age-matched females.

INTERVENTION

Two weeks of VLCD (2500 kJ/d).

MAIN OUTCOME MEASURES

Metabolic parameters, circulating cytokines, hormones, and mRNA expression of 39 genes in sc adipose tissue (SCAT) and PM.

RESULTS

Both T2DM and OB group had significantly increased serum concentrations of circulating proinflammatory factors (C-reactive protein, TNFα, IL-6, IL-8), mRNA expression of macrophage antigen CD68 and proinflammatory chemokines (CCL-2, -3, -7, -8, -17, -22) in SCAT and complementary chemokine receptors (CCR-1, -2, -3, -5) and other proinflammatory receptors (toll-like receptor 2 and 4, TNF receptor superfamily 1A and 1B, IL-6R) in PM, with OB group showing less pronounced chemoattracting and proinflammatory profile compared to T2DM group. In T2DM patients VLCD decreased body weight, improved metabolic profile, and decreased mRNA expression of up-regulated CCRs in PM and chemokines [CCL 8, chemokine (C-X-C motif) ligand 10] in SCAT. VLCD markedly increased mRNA expression of T-lymphocyte attracting chemokine CCL-17 in SCAT.

CONCLUSION

Obese patients with and without T2DM have increased mRNA expression of chemotactic and proinflammatory factors in SCAT and expression of corresponding receptors in PM. Two weeks of VLCD significantly improved this profile in T2DM patients.

Serum concentrations and tissue expression of a novel endocrine regulator fibroblast growth factor-21 in patients with type 2 diabetes and obesity

OBJECTIVE

Fibroblast growth factor-21 (FGF21) is a novel endocrine and paracrine regulator of metabolic homeostasis. The aim of our study was to measure its serum concentrations in patients with obesity, obesity and type 2 diabetes mellitus (T2DM) and healthy subjects (C), and to assess the changes of its circulating levels and mRNA expression after dietary and pharmacological interventions.

DESIGN

We measured biochemical parameters, serum FGF21, adiponectin, leptin and insulin levels by commercial ELISA and RIA kits, and mRNA expression in the liver, subcutaneous and visceral fat by RT PCR in 26 obese patients, 11 T2DM patients and 32 control subjects. The interventions were acute hyperinsulinaemia during isoglycaemic-hyperinsulinaemic clamp, very low calorie diet (VLCD) and 3 months treatment with PPAR-alpha agonist fenofibrate.

RESULTS

Baseline serum FGF21 levels were significantly higher in both obese and T2DM patients relative to healthy controls. FGF21 levels in obesity did not significantly differ from T2DM group. Both 3 weeks of VLCD and 3 months of fenofibrate treatment significantly increased FGF21 levels. FGF21 mRNA expression in visceral fat was twofold higher in obesity relative to C group, while it did not differ in subcutaneous fat. VLCD significantly increased FGF21 mRNA expression in subcutaneous fat of obesity. 3-h hyperinsulinaemia during the clamp increased FGF21 levels in T2DM but not in C group.

CONCLUSION

An increase in FGF21 levels after VLCD and fenofibrate treatment may contribute to positive metabolic effect of these interventions and suggests the possibility of direct positive metabolic effects of FGF21 in humans.

Improvement of insulin sensitivity after peroxisome proliferator-activated receptor-alpha agonist treatment is accompanied by paradoxical increase of circulating resistin levels

We studied the effect of peroxisome proliferator-activated receptor-alpha (PPAR-alpha) activation on serum concentrations and tissue expression of resistin, adiponectin, and adiponectin receptor-1 and -2 (AdipoR1 and AdipoR2) mRNA in normal mice and mice with insulin resistance induced by lipogenic, simple-carbohydrate diet (LD). Sixteen weeks of LD feeding induced obesity with liver steatosis and increased insulin levels but did not significantly affect circulating adiponectin or resistin. Treatment with PPAR-alpha agonist fenofibrate decreased body weight and fat pad weight and ameliorated liver steatosis in LD-fed mice with concomitant reduction in blood glucose, free fatty acid, triglyceride, serum insulin levels, and homeostasis model assessment index values. Euglycemic-hyperinsulinemic clamp demonstrated the development of whole-body and liver insulin resistance in LD-fed mice, which were both normalized by fenofibrate. Fenofibrate treatment markedly increased circulating resistin levels on both diets and adiponectin levels in chow-fed mice only. Fat adiponectin mRNA expression was not affected by fenofibrate treatment. Resistin mRNA expression increased in subcutaneous but not gonadal fat after fenofibrate treatment. In addition to fat, a significant amount of adiponectin mRNA was also expressed in the muscle. This expression markedly increased after fenofibrate treatment in chow- but not in LD-fed mice. Adipose tissue expression of AdipoR1 mRNA was significantly reduced in LD-fed mice and increased after fenofibrate treatment. In conclusion, PPAR-alpha activation ameliorated the development of insulin resistance in LD-fed mice despite a major increase in serum resistin levels. This effect could be partially explained by increased AdipoR1 expression in adipose tissue after fenofibrate treatment.