Metformin induces glucose uptake in human preadipocyte‐derived adipocytes from various fat depots

Abstract

To evaluate the effect of metformin on basal and insulin-induced glucose uptake in subcutaneous and visceral preadipocyte-derived adipocytes from obese and non-obese patients, preadipocytes were obtained from subcutaneous and visceral fat depots during abdominal surgery. Differentiation efficiency was evaluated by measurement of intracellular triglyceride accumulation. Preadipocyte-derived adipocytes were treated with metformin (1 mM) for 24 h with or without the addition of insulin (100 nM) for 20 min and glucose uptake was measured. In cells from each donor, intracellular triglyceride accumulation was more abundant in subcutaneous preadipocyte-derived adipocytes than in visceral preadipocyte-derived adipocytes (p < 0.001). Insulin stimulated glucose uptake in subcutaneous preadipocyte-derived adipocytes from both non-obese and obese patients (p < 0.001 vs. basal). In visceral preadipocyte-derived adipocytes, insulin did not increase basal glucose uptake. In subcutaneous preadipocyte-derived adipocytes from non-obese and obese patients, metformin alone increased glucose uptake to 2.7 +/- 0.2 (p < 0.001) and 2.1 +/- 0.1 fold (p < 0.001) respectively. Metformin increased glucose uptake in visceral preadipocyte-derived adipocytes from non-obese (1.7 +/- 0.1 fold vs. basal, p < 0.001) and obese (2.0 +/- 0.2 fold vs. basal, p < 0.001) patients. Combined treatment with metformin and insulin increased glucose uptake in subcutaneous preadipocyte-derived adipocytes from both non-obese and obese patients (p < 0.001 vs. insulin alone). In preadipocyte-derived adipocytes glucose uptake is induced by metformin independent of the fat depot origin of the preadipocytes (subcutaneous or visceral) and the obesity state of the patients (non-obese or obese). In adipocytes, metformin seems to induce glucose uptake independent of insulin suggesting an alternative mechanism of action of this drug.

AMP-activated protein kinase is activated in adipose tissue of individuals with type 2 diabetes treated with metformin: a randomised glycaemia-controlled crossover study

“…The data in the current study represent, to the authors' knowledge, the first report of the effect of metformin on insulin-stimulated glucose transport in 3T3-L1 adipocytes. Previous studies in human adipocytes differentiated from mesenchymal stem cells or pre-adipocytes indicate that metformin stimulation for 24 h increased basal and insulinstimulated glucose uptake [22,42], yet incubation of adipocytes isolated from individuals with type 2 diabetes with metformin for 1 h has been reported to have no effect on basal or insulin-stimulated glucose uptake [38]. Increased levels of GLUT4 protein have been associated with AMPK activation in cultured adipocytes [30], and metformin has been reported to increase mRNA expression of GLUT4 (also known as SLC2A4) in adipose from women with polycystic ovary syndrome [43], yet the amount of GLUT4 protein was unaltered in the current study in either human adipose tissue or 3T3-L1 adipocytes, indicating that changes in GLUT4 expression are unlikely to underlie the difference in the fold stimulation by insulin.…”

Glucose-dependent insulinotropic polypeptide induces cytokine expression, lipolysis, and insulin resistance in human adipocytes

“…The study was approved by the local ethics committee, and informed consent was obtained from every patient. Stromal vascular cells were isolated as previously described (16) and expanded in DMEM-F12 containing 10% fetal calf serum (FCS), 5 ng/ml 2-fibroblast growth factor (FGF) (all from Lonza, Verviers, Belgium), sodium pyruvate, and penicillin-streptomycin (both from Invitogen, Basel, Switzerland) until confluence was reached. Differentiation into adipocytes was induced by incubating confluent cells in DMEM-F12 containing 3% FCS, 50 mg/ml gentamycin solution, and 30 mM HEPES (all from Invitrogen) and supplements as follows: 250 M 3-isobutyl-1-methylxanthine (IBMX), 1 M dexamethasone, 0.2 nM 3,3,5-triiodo-L-thyronine, 100 mM L-ascorbic acid, 8 g/ml D-biotin, 15 mM D-pantothenat (all from Sigma-Aldrich, Buchs, Switzerland), 5 M transferrin (Merck, Dietikon, Switzerland), 100 nM insulin (Novo Nordisk, Küsnacht, Switzerland), and 1 M rosiglitazone (GlaxoSmithKline, Worthing, UK).…”

Both inflammatory and classical lipolytic pathways are involved in lipopolysaccharide-induced lipolysis in human adipocytes

“…The pre-adipocytes were expanded in vitro in DMEM containing 10% FCS and 2 ng/ml 2-FGF (Lubio Science, Luzern, Switzerland) until confluence and subjected to an adipogenic differentiation medium for 14 d as previously described. 13 For experimental purposes, cells were washed twice with warm phosphate-buffered saline (PBS) and kept for 48 h in a low-glucose medium (1.8 g/l glucose): DMEM (Lonza, Verviers, Belgium) supplemented with nutrient mixture F-12 (Lubio Science), gentamycin (50 mg/ml), L-ascorbic acid (100 nM), biotin (8 mg/ml), D-pantothenate (15 mM), HEPES (15 nM) and 3% FCS. Then, cells were treated with LPS (Sigma Aldrich, Buchs, Switzerland) from 1 ng/ml to 1 mg/ml for 24 h. Additionally, if co-treated, adipocytes were pre-treated for 1 h before LPS stimulation with DMSO (vehicle), 80 mM NF-kB inhibitor (pyrrolidine dithiocarbamate; PDTC), 100 mM IKKb inhibitor (sc-514), 20 mM PKA inhibitor (H-89; Merck Chemicals, Nottingham, UK), 10 mM MAPK inhibitor (U0126), 100 mM orlistat, 1mM isoproterenol, 10 mM milrinone (Sigma-Aldrich) and 20 mM CAY10499 (Cayman Chemicals, Ann Arbor, MI, USA).…”