Compromised browning plasticity of primary subcutaneous adipocytes derived from overweight Chinese adults

Abstract

Purpose: People with obesity have a compromised browning capacity of adipose tissue when faced with sympathetic stimuli. This study aimed to determine whether norepinephrine treatment can enhance the induction of precursor cells from human white adipose tissue to differentiate into adipocytes that express key markers of beige adipocytes, and if there is a difference in this capacity between normal weight and overweight individuals.

Methods: Stromal vascular cells derived from subcutaneous white adipose tissue of normal weight and overweight groups were induced to differentiation, with or without norepinephrine, into adipocytes. Oxygen consumption rate, lipolysis, the expression of uncoupling protein 1 and other thermogenic genes were compared between different adiposity and treatment groups.

Results: Peroxisome proliferator activated receptor γ- coactivator-1 alpha (PGC-1 α) and uncoupling protein 1 gene expression increased significantly in the normal weight group, but not in the overweight group, with norepinephrine treatment. The increments of lipolysis and oxygen consumption rate were also higher in adipocytes from the normal weight group with norepinephrine treatment, as compared with those of the overweight group. PR domain containing protein 16 (PRDM 16) gene expression was higher in the normal weight group compared with that in the overweight group, while there were no significant changes found with norepinephrine treatment in either the normal weight or overweight group.

Conclusions: Adipogenic precursor cells derived from overweight individuals were less prone to differentiate into beige-like adipocytes when facing sympathetic stimuli than normal weight ones, resulting in the compromised sympathetic-induced browning capacity in subcutaneous white adipose tissue in overweight individuals, which occurred before the onset of overt obesity.

Keywords: Adipocyte browning; Chinese; Norepinephrine; Overweight; Subcutaneous adipose tissue.

Fig. 1

EBf2 expression in adipose-derived vascular stromal cells. Fold change in EBf2 gene expression of vascular stromal cells derived from adipose tissue in the normal weight (NW) and overweight (OW) groups (Values were mean ± SD; NW group expression level normalized to 1.0; n = 25 for the NW and OW group; experiments were repeated three times for each sample; *P < 0.05 NW vs OW group). NW group normal weight group, OW group overweight group

Fig. 2

Oil-red O-staining of differentiated adipocytes (day 14). Before (a) and after differentiation cells (b normal weight group; c overweight group) were fixed and stained with oil red-O; images shown are 20 × magnification

Fig. 3

Fold changes of indicated genes during adipocyte differentiation. Normal-weight (NW) compared to the overweight (OW) group and norepinephrine (NE) treatment compared to control (con) group. PGC-1α (a) and PRDM16 (b) gene expression in the NW-con group at day 0 was normalized to 1, and UCP-1 gene expression (c) in the NW-con group at day 5 was normalized to 1. (Values were mean ± SD; n = 10 for the NW and OW group; experiments were repeated three times for each sample; ^#P < 0.05 NW vs OW group; *P < 0.05 control vs NE treatment). NW-con normal weight control group, NW-NE normal weight norepinephrine treatment group, OW-con overweight control group, OW-NE overweight norepinephrine treatment group

Fig. 4

UCP-1 protein content of differentiated adipocytes. Western-blot analysis of UCP-1 protein expression (a) and fold-change (b) in protein band density values of normal weight group (NW) and overweight group (OW) with (NE) and without (control) norepinephrine treatment, OW-con group values normalized to 1.0 (Values were mean ± SD; n = 10 for the NW-NE, NW-con, OW-NE and OW-con group; ^#P < 0.05 NW vs OW group; *P < 0.05 control vs NE treatment).OW-con overweight control group, NW-con normal weight control group, OW-NE overweight norepinephrine treatment group, NW-NE normal weight norepinephrine treatment group

Fig. 5

Oxygen consumption rate in differentiated adipocytes. The differentiated adipocytes derived from the normal weight (NW) and overweight (OW) groups treated with (NW-NE and OW-NE) or without (NW-con and OW-con) norepinephrine were used to detect oxygen consumption rate (OCR). The oxygen consumption rate (OCR) was measured at baseline and followed by sequential stimulation with oligomycin, FCCP, and antimycin A. Subtracting antimycin A-insensitive OCR (non-mitochondrial respiration) from baseline OCR reveals basal OCR, oligomycin was added to render uncoupled OCR, and FCCP rates represent maximal respiratory capacity, three data points were collected from each period, and mean value of the three points were calculated for data analysis. Experiments were repeated at least 3 times. a Basal, uncoupled and maximal OCR values were normalized by the total-cell protein concentration and compared between different groups (b). (Values were mean ± SD; n = 10 for the NW-NE, NW-con, OW-NE and OW-con groups; data used for analysis were mean values of four replicate wells for each sample. ^#P < 0.05 NW vs OW group; *P < 0.05 control vs NE treatment). NW-NE normal weight norepinephrine treatment group, NW-con normal weight control group, OW-NE overweight norepinephrine treatment group, OW-con overweight control group, OCR oxygen consumption rate

Fig. 6

Lipolysis analysis of differentiated adipocytes. Glycerol concentration was measured in the media to determine rates of lipolysis after differentiated cells derived from the normal weight (NW) and overweight (OW) groups were treated with PBS (NW-con and OW-con) or 1 μM norepinephrine (NW-NE and NW-NE) for 6 h (Values were mean ± SD; n = 10 for NW-NE, NW-con, OW-NE and OW-con groups; data used for analysis were mean values of three replicate experiments for each sample; ^#P < 0.05 NW vs OW group; *P < 0.05 con vs NE treatment). NW normal weight group, OW overweight group