APS: Insulin Resistance Responds to Laparoscopic Gastric Banding

WASHINGTON, May 1 -- Gastric banding puts the squeeze on insulin resistance, even when the patient remains obese.

Interim results of a small study of patients who underwent laparoscopic gastric banding showed that insulin resistance was reduced by 60% within six months of the surgery, reported Joan F. Carroll, Ph.D., of the University of North Texas Health Science Center in Fort Worth, and colleagues.

The change in insulin resistance profiles came largely because of a 50% reduction in fasting insulin concentrations, with no change in fasting glucose concentrations, the investigators said at the American Physiological Society meeting here.

The authors conducted a study to determine whether laparoscopic gastric banding could have beneficial metabolic effects similar to those seen with Roux-en-Y gastric bypass.

They recruited 29 volunteers (12 men and 17 women) from a local surgical practice. All patients had been screened and deemed suitable candidates for bariatric surgery. The patients were evaluated at baseline prior to surgery and at six months after surgery for body composition, blood pressure, metabolic risk factors, and insulin resistance measured with homeostasis model assessment.

Metabolic risk biomarkers included fasting serum lipids, insulin, glucose, cardiac C-reactive protein, fatty acids, homocysteine, glycosylated hemoglobin A1 (HbA1c), apolipoprotein A1, apolipoprotein B, and resting blood pressure.

As expected, the researchers found that at baseline, men were heavier and had greater waist circumferences, more visceral adipose tissue (measured at the L4-L5 spinal level), and more total visceral adipose tissue. Men also had higher HbA1c levels, whereas women had higher a percentage of body fat.

Six months after surgery the entire group had a reduction in mean body weight from 275 to 233 pounds (15% decrease), a 14% reduction in body mass index (from 43.4 to 37.3), a 13% reduction in the percentage of body fat (from 49% to 43%), a 13% loss in waist circumference (from 53 inches to 46), and a 10% reduction in hip circumference (from 57 inches to 51).

In addition, total visceral adipose tissue tended to decrease by 20% (from 6.5 kg to 5.2 kg) but the change did not reach statistical significance.

Waist-to-hip ratios decreased in women only, from 0.92 at baseline to 0.86 at six months, and there was a trend toward decrease in HbA1c, from 5.8% to 5.6% which did not reach significance.

Total visceral adipose tissue was significantly reduced in men only, dropping from 8.7 kg before surgery to 6.6 kg after. Diastolic blood pressure dropped from 81 mm Hg to 75 mg Hg, and the inflammatory marker C-reactive protein went from 8.3 mg/L pre-op to 4.7 mg/L post-op but neither change reached statistical significance.

The authors noted that despite the significant reduction in insulin resistance, other factors such as blood pressure and lipids remained largely unchanged, which could be because the patients had average values at baseline, despite being obese.

"Longer range follow-up and/or larger sample size may be needed to demonstrate benefits of laparoscopic gastric banding surgery in risk factors other than body composition or insulin resistance," they wrote.