Figure 1.

Bicarbonate increases adipocyte respiration independently of insulin sensitivity. (A) 3T3-L1 adipocytes were incubated with or without bicarbonate (10 mM) and respiration was assessed using the XFp Analyzer. Following basal measurements (Bas), cells were sequentially treated with insulin (Ins), oligomycin (Oligo), Bam15, and rotenone/antimycin A (Rot/AA). Data presented as mean + SEM, from n = 4 separate experiments. (B) 3T3-L1 adipocytes were assayed for 2-deoxyglucose (2DOG) uptake for a range of insulin concentrations, in the presence or absence of bicarbonate (10 mM). Data presented as mean ± SEM, from at least n = 3 separate experiments for each insulin concentration. (C) The data from (B) were used to calculate basal uptake, maximal response (maximal uptake – basal uptake), and the insulin EC₅₀. Data presented as mean ± SEM. Responses are in pmol/mg/min and EC₅₀ is in nM. (D) 3T3-L1 adipocytes were incubated in Media B (except with 10 mM glucose) for 1 h, in the presence of insulin (100 nM) with or without bicarbonate (10 mM). Following treatment, glucose consumption was measured by assaying the glucose content of the media. Data presented as mean ± SEM, from n = 3 separate experiments. * p<0.05, ** p<0.01, using the two-tailed t-test.