Ectopic fat storage in the pancreas using 1H-MRS: importance of diabetic status and modulation with bariatric surgery-induced weight loss.
Gaborit B., Abdesselam I., Kober F., Jacquier A., Ronsin O., Emungania O., Lesavre N., Alessi M-C., Martin JC., Bernard M., Dutour A.
OBJECTIVES: Recent literature suggests that ectopic fat deposition in the pancreas may contribute to endocrine and exocrine organ dysfunction, such as type 2 diabetes (T2D), pancreatitis or pancreatic cancer. The aim of this study was to determine factors associated with pancreatic triglyceride content (PTGC), and to investigate the impact of bariatric surgery on ectopic fat pads, pancreatic fat (PTGC) and hepatic fat (HTGC). SUBJECTS: In all, 45 subjects (13 lean, 13 obese nondiabetics and 19 T2D, matched for age and gender) underwent 1H-magnetic resonance spectroscopy, computed tomography of the visceral abdominal fat, metabolic and lipidomic analysis, including insulin-resistance homeostasis model assessment (HOMA-IR), insulin-secretion homeostasis model assessment (HOMA-B) and plasma fatty-acid composition. Twenty obese subjects were reassessed 6 months after the bariatric surgery. RESULTS: PTGC was significantly higher in type 2 diabetic subjects (23.8±3.2%) compared with obese (14.0±3.3; P=0.03) and lean subjects (7.5±0.9%; P=0.0002). PTGC remained significantly associated with T2D after adjusting for age and sex (β=0.47; P=0.004) or even after adjusting for waist circumference, triglycerides and HOMA-IR (β=0.32; P=0.04). T2D, C18:1n-9 (oleic acid), uric acid, triglycerides and plasminogen activator inhibitor-1 were the five more important parameters involved in PTGC prediction (explained 80% of PTGC variance). Bariatric surgery induced a huge reduction of both HTGC (-51.2±7.9%) and PTGC (-43.8±7.0%) reaching lean levels, whereas body mass index remained greatly elevated. An improvement of insulin resistance HOMA-IR and no change in HOMA-B were observed after bariatric surgery. The PTGC or HTGC losses were not correlated, suggesting tissue-specific mobilization of these ectopic fat stores. CONCLUSION: Pancreatic fat increased with T2D and drastically decreased after the bariatric surgery. This suggests that decreased PTGC may contribute to improved beta cell function seen after the bariatric surgery. Further, long-term interventional studies are warranted to examine this hypothesis and to determine the degree to which ectopic fat mobilization may mediate the improvement in endocrine and exocrine pancreatic functions.