Hypoxia Alters the Expression of Dipeptidyl Peptidase 4 and Induces Developmental Remodeling of Human Preadipocytes

Figure 4

Differentiation and hypoxia reduce the shedding of DPP4 from human preadipocytes cultured in vitro. (a) Normalized DPP4 protein concentration in conditioned medium of cells at different stages of differentiation from preadipocytes to mature adipocytes cultured under normoxic (black bars) and hypoxic (white bars) environmental conditions. (b) Normalized DPP4 protease activity in conditioned medium of cells at different stages of differentiation from human preadipocytes to mature adipocytes cultured in normoxic (black bars) and hypoxic (white bars) environmental conditions. Data are normalized to the total cell number in the sample and presented as mean values ± SE. Asterisks above the white bars denote significant difference between hypoxic versus normoxic condition on the same differentiation day (Student’s -test; ; ; ); # under the bars denotes significant difference compared with day 0 for respective oxygenation condition (one-way ANOVA; ). (c) Correlation between the concentration of DPP4 in the conditioned media and its activity under normoxic (black dots) and hypoxic (open dots) conditions (, slope coefficient; , correlation coefficient). The equation of regression lines is as follows: DPP4 activity [fmol/min/cell] = () × DPP4 concentration [pg/μL/cell] − () [fmol/min/cell] for the correlation in normoxia and DPP4 activity [fmol/min/cell] = () × DPP4 concentration [pg/μL/cell] − () [fmol/min/cell] for the correlation in hypoxia. The slopes are significantly different (), whereas the intercepts are similar and not different from 0.

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