The relationship of omental and subcutaneous adipocyte size to metabolic disease in severe obesity.
OBJECTIVE
Several studies have reported the existence of a subgroup of obese individuals with normal metabolic profiles. It remains unclear what factors are responsible for this phenomenon. We proposed that adipocyte size might be a key factor in the protection of metabolically healthy obese (MHO) individuals from the adverse effects of obesity.


METHODS
Thirty-five patients undergoing bariatric surgery were classified as MHO (n = 15) or metabolically unhealthy obese (MUO, n = 20) according to cut-off points adapted from the International Diabetes Federation definition of the metabolic syndrome. Median body mass index (BMI) was 48 (range 40-71).


RESULTS
There was a moderate correlation between omental adipocyte size and subcutaneous adipocyte size (r = 0.59, p<0.05). The MHO group had significantly lower mean omental adipocyte size (80.9+/-10.9 microm) when compared with metabolically unhealthy patients (100.0+/-7.6 microm, p<0.0001). Mean subcutaneous adipocyte size was similar between the two groups (104.1+/-8.5 microm versus 107.9+/-7.1 microm). Omental, but not subcutaneous adipocyte size, correlated with the degree of insulin resistance as measured by HOMA-IR (r = 0.73, p<0.0005), as well as other metabolic parameters including triglyceride/HDL-cholesterol ratio and HbA1c. Twenty-eight patients consented to liver biopsy. Of these, 46% had steatohepatitis and fibrosis. Fifty percent (including all the MHO patients) had steatosis only. Both omental and subcutaneous adipocyte size were significantly associated with the degree of steatosis (r = 0.66, p<0.0001 and r = 0.63, p<0.005 respectively). However, only omental adipocyte size was an independent predictor of the presence or absence of fibrosis.


CONCLUSIONS
Metabolically healthy individuals are a distinct subgroup of the severely obese. Both subcutaneous and omental adipocyte size correlated positively with the degree of fatty liver, but only omental adipocyte size was related to metabolic health, and possibly progression from hepatic steatosis to fibrosis.
O'Connell
Jean
J
Obesity Research Group, Education and Research Centre, St Vincent's University Hospital, Dublin, Ireland. jeanoco@gmail.com
Lynch
Lydia
L
Cawood
Tom J
TJ
Kwasnik
Anna
A
Nolan
Niamh
N
Geoghegan
Justin
J
McCormick
Aiden
A
O'Farrelly
Cliona
C
O'Shea
Donal
D
D017667:Adipocytes / Q000473:pathology*; D000328:Adult; D015992:Body Mass Index; D048429:Cell Size; D005234:Fatty Liver; D005260:Female; D006801:Humans; D007333:Insulin Resistance; D008297:Male; D008659:Metabolic Diseases / Q000175:diagnosis* / Q000473:pathology; D024821:Metabolic Syndrome / Q000175:diagnosis / Q000473:pathology; D008875:Middle Aged; D009852:Omentum / Q000473:pathology*; D050151:Subcutaneous Fat / Q000473:pathology*