Increased expression of eNOS protein in omental versus subcutaneous adipose tissue in obese human subjects.

OBJECTIVE: To investigate the expression of eNOS and iNOS mRNA and protein in adipose tissue from subcutaneous (s.c.) and omental adipose tissue of obese subjects.
DESIGN: Subcutaneous and omental adipose tissue was obtained from subjects undergoing weight reduction surgery. Messenger RNA and protein levels were measured in tissue extracts and related to basal lipolysis, which was measured in isolated adipocytes from the same subjects.
SUBJECTS: Eight overweight but otherwise healthy male subjects (age 43.4+/-10.3 y, BMI 39+/-3.5 kg/m(2), mean+/-s.e.m.). MEASUREMENTS: For mRNA detection a competitive reverse transcription polymerase chain reaction method was used while protein was detected by Western blot. Glycerol release was determined in isolated adipocytes using a standard luminometric assay.
RESULTS: Tissue mRNA levels for eNOS in s.c. tissue were 6098+/-1969 amol/mg RNA and in omental tissue 6987+/-2914 amol/mg RNA (mean+/-s.e.m., P=0.75). iNOS mRNA levels were substantially lower; in s.c. tissue 227+/-127 amol/mg RNA and in omental tissue 245+/-162 amol/mg RNA (P=0.8). In Western blot, eNOS protein levels in s.c. and omental tissue were 1.88+/-2.0 and 7.47+/-4.11 (OD/mm(2) 100 microg total protein, P=0.0063), respectively. iNOS protein was expressed at significantly lower levels and barely detectable in both s.c. and omental tissue. Basal rate of lipolysis was two times higher in s.c. compared to omental fat cells (P=0.028).
CONCLUSIONS: eNOS protein is markedly increased in omental compared to s.c. adipose tissue in human obese subjects, probably due to post-transcriptional mechanisms. Since basal lipolysis is much lower in omental vs s.c. adipose tissue it is possible that regionally increased NO production, primarily by eNOS, may be involved in the site difference of basal lipolysis in obese subjects.