Secretion of adiponectin multimeric complexes from adipose tissue explants is not modified by very low calorie diet

Abstract

Objective: Adiponectin is a protein abundantly secreted by the adipose tissue (AT). Plasma adiponectin levels are decreased in obese, insulin-resistant, and type 2 diabetic patients. Various multimeric complexes, i.e. high-, middle-, and low-molecular weight isoforms (HMW, MMW and LMW), are present in plasma. Here, we investigated the effect of weight reducing diet on the distribution of adiponectin isoforms in plasma and on their secretion in AT explants from obese subjects. Design: A total of 20 obese subjects (age 37.8G7.3 years, body mass index 33.9G5.0 kg/m 2 ) underwent eight weeks of very low-calorie diet (VLCD). A needle biopsy of subcutaneous abdominal AT and blood samples were taken before and after dietary intervention. AT explants were incubated in culture medium for 4 h. ELISA assay and western blot analyses were used to identify adiponectin complexes in culture media and in plasma. Results: The distribution of adiponectin polymers in plasma was different from that secreted in human AT explants. Before VLCD, the relative amount of HMW isoform was 75.5G9.1% of total adiponectin in culture media and 52.2G11.2% in plasma. Despite the diet-induced weight loss and improvement of insulin sensitivity, VLCD neither induced change in total adiponectin level nor in the ratio of HMW to total adiponectin in plasma and in culture media of AT explants. Conclusions: The profile of adiponectin polymeric isoforms secreted by AT explants into culture media differs from the plasma profile. A dietary intervention leading to weight loss and improvement of insulin sensitivity was not associated with modifications of AT secretion of total or HMW adiponectin.

Expansion of Bone Marrow Adipose Tissue During Caloric Restriction Is Associated With Increased Circulating Glucocorticoids and Not With Hypoleptinemia

“…Expression of Ero1l and Erp44 in tibial MAT was similarly unaffected, whereas Rab11fip1 expression was significantly higher in MAT of CRfed rabbits ( Figure 1E). These observations are consistent with the concept that adiponectin secretion from WAT does not increase during CR (54) and suggest that this is also true for tibial MAT. However, there is often a disparity between adiponectin transcript expression and circulating adiponectin levels (48,50,55).…”

“…Our data also support the possibility that secretion of adiponectin is not increased, at least based on the expression of known regulators of adiponectin secretion. Similar observations have been made for WAT of rodents and humans (47)(48)(49)(50)54); however, given the lack of hyperadiponectinemia and MAT expansion during CR in rabbits, the relevance of these observations to MAT of humans and other species remains unclear. This uncertainty, as well as the inability to isolate sufficient MAT from extensive CR rabbits, limited our ability to more comprehensively investigate the endocrine properties of MAT.…”

The impact of obesity on secretion of adiponectin multimeric isoforms differs in visceral and subcutaneous adipose tissue

“…14 We have shown and confirmed here that the profile of adiponectin multimers secreted by AT explants derived from needle biopsies of abdominal SAT differs from their plasma profile 26 and that the main isoform secreted by SAT and VAT explants is the HMW isoform. This is in agreement with other studies, showing HMW as the predominant form secreted by subcutaneous fat.…”

“…The length of incubation of AT explants with respect to adiponectin secretion was selected according to our previous experiments showing that the kinetic of total adiponectin secretion from AT explants is close to linearity in the interval between 1 h and 6 h of incubation. 26 Given the above mentioned kinetic, concentration at 4 h of AT explants incubation was chosen as representative for analysis of adiponectin isoforms secretion from different AT depots.…”

“…26,27 Briefly, proteins from plasma and conditioned media of explants were separated by native polyacrylamide gel electrophoresis (without b-mercaptoethanol and SDS) and transferred to nitrocellulose membranes. Membranes were incubated with anti-human adiponectin antibody (Rabbit Polyclonal Antibody, Biovendor Laboratory Medicine Inc., Modrice, Czech Republic), and with horseradish peroxidase --coupled goat anti-rabbit IgG (Jackson ImmunoResearch Europe Ltd, Cambridge, UK).…”