Improved metabolism and body composition beyond normal levels following gastric bypass surgery: a longitudinal study

BACKGROUND

The cardiometabolic risk profile improves following bariatric surgery. However, the degree of improvement in relation to weight-stable control subjects is unknown.

OBJECTIVES

To study the differences in cardiometabolic risk profile between formerly obese patients following Roux-en-Y gastric bypass (RYGB) surgery and control subjects.

METHODS

Subjects undergoing RYGB and reaching a BMI <30 kg m^-2 2 years postsurgery were matched with control subjects regarding age, sex and BMI. The following examinations were performed: insulin sensitivity measured by hyperinsulinaemic-euglycaemic clamp, insulin clearance, homeostatic model assessment of insulin resistance (HOMA-IR), lipid profile, inflammatory marker levels, dual-energy X-ray absorptiometry and subcutaneous adipose tissue cellularity (fat cell size and number).

RESULTS

Sixty-nine subjects undergoing RYGB were matched to a control subject. Insulin sensitivity measured by hyperinsulinaemic-euglycaemic clamp, blood pressure, inflammatory status and glucose, triglyceride and HDL cholesterol levels were comparable to values of control subjects. However, HOMA-IR (1.0 ± 0.5 vs. 1.3 ± 0.7, P = 0.005), insulin clearance (0.38 ± 0.08 vs. 0.34 ± 0.08 μL m^-2  min^-1 , P < 0.0001) and circulating levels of insulin (31 ± 15 vs. 37 ± 17 pmol L^-1 , P = 0.008), total cholesterol (4.1 ± 0.7 vs. 4.8 ± 0.9 mmol L^-1 , P < 0.0001) and LDL cholesterol (2.1 ± 0.6 vs. 2.9 ± 0.8 mmol L^-1 , P < 0.0001) were improved beyond the levels in matched control subjects. Furthermore, formerly obese subjects had higher lean and lower fat mass as well as a more benign type of adipose cellularity (hyperplasia with many small fat cells) compared to control subjects.

CONCLUSIONS

Subjects who underwent RYGB and reached a postobese state demonstrated a beneficial body composition, slightly increased insulin sensitivity as indirectly measured by HOMA-IR and higher insulin clearance, lower atherogenic lipid/lipoprotein levels and benign adipocyte morphology compared with control subjects who had never been obese. In line with previous results, our findings may in part explain why RYGB confers long-term protection against metabolic complications.

Waist circumference to assess reversal of insulin resistance following weight reduction after bariatric surgery: cohort and cross-sectional studies

OBJECTIVE

To validate the use of waist circumference to assess reversal of insulin resistance after weight loss induced by bariatric surgery.

DESIGN

In cross-sectional studies, threshold values for insulin resistance were determined with homeostasis model assessment of insulin resistance (HOMA-IR) (algorithm based on fasting plasma glucose and insulin) in 1018 lean subjects and by hyperinsulinemic euglycemic clamp (clamp) in 26 lean women. In a cohort study on 211 patients scheduled for bariatric surgery, HOMA-IR and waist circumference were measured before and 1.5-3 years after weight reduction. In a subgroup of 53 women, insulin sensitivity was also measured using clamp.

RESULTS

The threshold for insulin resistance (90th percentile) was 2.21 (mg dl(-1) fasting glucose × mU l(-1) fasting insulin divided by 405) for HOMA-IR and 6.118 (mg glucose per kg body weight per minute) for clamp. Two methods to assess reversal of insulin resistance by measuring waist circumference were used. A single cutoff value to <100 cm for waist circumference was associated with reversal of insulin resistance with an odds ratio (OR) of 49; 95% confidence interval (CI)=7-373 and P=0.0002. Also, a diagram based on initial and weight loss-induced changes in waist circumference in patients turning insulin sensitive predicted reversal of insulin resistance following bariatric surgery with a very high OR (32; 95% CI=4-245; P=0.0008). Results with the clamp cohort were similar as with HOMA-IR analyses.

CONCLUSIONS

Reversal of insulin resistance could either be assessed by a diagram based on initial waist circumference and reduction of waist circumference, or by using 100 cm as a single cutoff for waist circumference after weight reduction induced by bariatric surgery.

Prolonged exercise-induced stimulation of skeletal muscle glucose uptake is due to sustained increases in tissue perfusion and fractional glucose extraction

CONTEXT

The mechanisms behind the positive effects of physical activity on glucose metabolism in skeletal muscle and the time course of the effects need to be more elucidated.

OBJECTIVE

The aim was to examine the prolonged effects of an acute bout of one-legged exercise on local skeletal muscle glucose utilization and tissue perfusion.

DESIGN AND SETTING

Interstitial glucose concentration, local tissue perfusion, glucose uptake, and effects of insulin infusion were studied 12 h after an acute bout of exercise and without prior exercise.

PARTICIPANTS

Ten healthy subjects, five women and five men, participated in the study.

INTERVENTION

Microdialysis measurements, (133)Xe clearance, and a 2-h hyperinsulinemic euglycemic clamp were performed on two occasions.

MAIN OUTCOME MEASURES

We measured interstitial glucose concentration and tissue perfusion in the quadriceps femoris muscle of both legs.

RESULTS

Tissue perfusion (3.3 ± 0.6 ml × 100 g(-1) × min(-1) vs. 1.4 ± 0.2 ml × 100 g(-1) × min(-1); P = 0.007) and basal glucose uptake (2.3 ± 0.5 μmol × 100 g(-1) × min(-1) vs. 0.9 ± 0.2 μmol × 100 g(-1) × min(-1); P = 0.006) were increased in the leg that had exercised compared to the resting leg; the findings in the resting leg were comparable to those in the control experiment without prior exercise. The relative effect of insulin on fractional skeletal muscle glucose uptake was the same in all experimental settings, and insulin did not affect tissue perfusion.

CONCLUSIONS

The prolonged stimulatory effect of physical exercise on skeletal muscle glucose uptake was mediated via vascular effects combined with an increase in basal glucose transport independent of enhancement of insulin responses.

Regional impact of adipose tissue morphology on the metabolic profile in morbid obesity

AIMS/HYPOTHESIS

The aim of this study was to determine whether the mean size of fat cells in either visceral or subcutaneous adipose tissue has an impact on the metabolic and inflammatory profiles in morbid obesity.

METHODS

In 80 morbidly obese women, mean visceral (omental) and subcutaneous fat cell sizes were related to in vivo markers of inflammation, glucose metabolism and lipid metabolism.

RESULTS

Visceral, but not subcutaneous, adipocyte size was significantly associated with plasma apolipoprotein B, total cholesterol, LDL-cholesterol and triacylglycerols (p ranging from 0.002 to 0.015, partial r ranging from 0.3 to 0.4). Subcutaneous, but not visceral, adipocyte size was significantly associated with plasma insulin and glucose, insulin-induced glucose disposal and insulin sensitivity (p ranging from 0.002 to 0.005, partial r ranging from -0.34 to 0.35). The associations were independent of age, BMI, body fat mass or body fat distribution. Adipose tissue hyperplasia (i.e. many small adipocytes) in both regions was significantly associated with better glucose, insulin and lipid profiles compared with adipose hypertrophy (i.e. few large adipocytes) in any or both regions (p ranging from <0.0001 to 0.04). Circulating inflammatory markers were not associated with fat cell size or corresponding gene expression in the fat cell regions examined.

CONCLUSIONS/INTERPRETATION

In morbidly obese women region-specific variations in mean adipocyte size are associated with metabolic complications but not systemic or adipose inflammation. Large fat cells in the visceral region are linked to dyslipidaemia, whereas large subcutaneous adipocytes are important for glucose and insulin abnormalities. Hyperplasia (many small adipocytes) in both adipose regions may be protective against lipid as well as glucose/insulin abnormalities in obesity.