Endoplasmic reticulum stress markers are associated with obesity in nondiabetic subjects.
OBJECTIVE
Adipocyte and hepatocyte endoplasmic reticulum (ER) stress response is activated in dietary and genetic models of obesity in mice. We hypothesized that ER stress was also activated and associated with reduced insulin sensitivity (SI) in human obesity.


METHODS
We recruited 78 healthy, nondiabetic individuals over a spectrum of body mass index (BMI) who underwent oral and iv glucose tolerance tests, and fasting sc adipose and muscle biopsies. We tested expression of 18 genes and levels of total and phosphorylated eukaryotic initiation factor 2alpha, c-jun, and c-Jun N-terminal kinase 1 in adipose tissue. We compared gene expression in stromal vascular and adipocyte fractions in paired samples from 22 individuals, and tested clustering on gene and protein markers.


RESULTS
Adipocyte expression of most markers of ER stress, including chaperones downstream of activating transcription factor 6, were significantly correlated with BMI and percent fat (r>0.5; P<0.00001). Phosphorylation of eukaryotic initiation factor 2alpha but not of c-Jun N-terminal kinase 1 or c-jun was increased with obesity. ER stress response (as elsewhere) was also increased with obesity in a second set of 86 individuals, and in the combined sample (n=161). The increase was only partially attributable to the stromal vascular fraction and macrophage infiltration. ER stress markers were only modestly correlated with S(I). Clustering algorithms supported ER stress activation with high BMI but not low SI.


CONCLUSIONS
Multiple markers of ER stress are activated in human adipose with obesity, particularly for protective chaperones downstream of activating transcription factor 6alpha.
Sharma
Neeraj K
NK
Medicine and Research Services, Central Arkansas Veterans Healthcare System, University of Arkansas for Medical Sciences, Endocrinology 111J-1/LR, John L. McClellan Memorial Veterans Hospital, 4300 West 7th Street, Little Rock, Arkansas 72205, USA.
Das
Swapan K
SK
Mondal
Ashis K
AK
Hackney
Oksana G
OG
Chu
Winston S
WS
Kern
Philip A
PA
Rasouli
Neda
N
Spencer
Horace J
HJ
Yao-Borengasser
Aiwei
A
Elbein
Steven C
SC
D000273:Adipose Tissue / Q000033:anatomy & histology / Q000502:physiology; D000293:Adolescent; D000328:Adult; D000818:Animals; D015992:Body Mass Index; D004721:Endoplasmic Reticulum / Q000502:physiology*; D005951:Glucose Tolerance Test; D006801:Humans; D051379:Mice; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology; D009765:Obesity / Q000503:physiopathology*; D010750:Phosphoproteins / Q000235:genetics; D012016:Reference Values; D013312:Stress, Physiological; D049629:Waist-Hip Ratio; D055815:Young Adult
D010750:Phosphoproteins