Effect of adiposity on tissue-specific adiponectin secretion.

Circulating adiponectin levels are lower in individuals with increased BMI and central adiposity. However, they are paradoxically higher in those with peripheral adiposity. We hypothesized that adiponectin secretion from central and peripheral adipose tissue depots may be associated with adiposity levels and its distribution. A total of 55 subjects (69% women) undergoing elective abdominal surgery (mean age: 53 ± 13 years) were recruited. Health history, anthropometrics, and cardiovascular disease risk factor measurements were obtained. Subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) samples were obtained and cultured. Media was collected after 24hr and adiponectin released into the medium was measured using ELISA. We found that mean adiponectin levels from SAT and VAT in all subjects were 17.14±15.27 vs. 15.21±14.28 pg/ml/mg of tissue respectively (p = ns). However, adiponectin secretion from VAT correlated negatively with BMI (r = -0.31, p = 0.01), whereas there was no relationship with SAT (r = 0.08 p = 0.61). Similarly, waist circumference and estimated VAT percentage were both negatively correlated with VAT secretion of adiponectin (r = -0.35, p = 0.01 and r = -0.36, p = 0.02 respectively). These negative correlations were significant only in women on gender-stratified analyses. Adiponectin secretion from VAT decreases with increases in adiposity, while SAT secretion remains unchanged, especially in women. This observation may explain lower circulating adiponectin levels in individuals with central obesity. Further studies are needed to explore the mechanism behind this discrepant adiponectin secretion from SAT and VAT with increases in BMI, particularly among women.

Stroke and atrial fibrillation following cardiac surgery.

OBJECTIVE: Stroke is an occasional devastating complication of cardiac surgery. Transient atrial fibrillation (AF) is a frequent complication of cardiac surgery. Emboli originating from the fibrillating left atrium are a known cause of stroke in the non-surgical setting. The purpose of this quality improvement initiative, conducted by the Wausau Heart Institute, was to characterize strokes after cardiac surgery and to investigate the relationship between AF and the occurrence of postoperative strokes. METHODS: We conducted a retrospective record review of all patients undergoing cardiac surgery utilizing cardiopulmonary bypass without associated carotid surgery at our institution between January 1, 1993 and June 30, 1999. The occurrence of strokes and AF was noted. The timing of the AF (duration and relationship to surgery) was recorded. RESULTS: Of the 2104 eligible patients, strokes occurred in 68 (3.2%). In 18 patients (27%), stroke was immediately apparent as the patient recovered from anesthesia (intra-operative stroke). Fifty of the 68 strokes (74%) were acquired following the immediate operative period after the patient awoke from anesthesia neurologically intact (postoperative stroke). Postoperative stroke occurred in 2.1% of patients undergoing coronary bypass surgery only, in 2.2% if valve surgery only was performed, and 4.6% if both valve and bypass surgery were performed. AF occurred in 700 patients (33%). The incidence of postoperative stroke was 5.4% in patients with AF and 0.89% in those without AF (P < 0.001). Of those patients suffering a postoperative stroke, 76% had AF following cardiac surgery, compared to 32% if a postoperative stroke did not occur (P < 0.001). Carotid bruits were present in 7 (14%) of the patients with postoperative stroke. Carotid ultrasound studies were performed in 32 patients (63%) and a lesion of > 70% was found in 8 patients (25%). Cerebral lesions contralateral to the stenotic carotid artery occurred in 3 of these 8 patients. CONCLUSION: Most strokes complicating cardiac surgery occur in patients without significant carotid disease, and are acquired after the patient awakens neurologically intact. The high incidence of postoperative AF in these patients suggests a possible embolic cause for some of the strokes. As such, some postoperative strokes may be preventable.