Concordance of in vivo microdialysis and in vitro techniques in the studies of adipose tissue metabolism.

BACKGROUND: Adipose tissue metabolism can be investigated directly in vivo by microdialysis and indirectly in vitro using isolated adipocytes. The in vitro studies are relatively easy to make and they give information about specific tissue metabolism. The in vivo studies, on the other hand, are supposed to give relevant data about tissue physiology interacting with other metabolic systems at the body level. OBJECTIVE: To investigate the concordance between the results on responsiveness to stimulation of lipolysis from in vivo microdialysis and in vitro isolated adipocytes. SUBJECTS: Altogether 22 massively obese otherwise healthy subjects (seven men and 15 women, age 41 (26-55) y, BMI 51.5 (37.5-73.9)kg/m2, mean (range)) going through the gastric banding operation participated in the study. METHODS: The microdialysis study was done after an overnight fast at rest. Lipolysis was stimulated with isoprenaline that was perfused into the subcutaneous abdominal adipose tissue. Local blood flow was estimated by ethanol dilution method. Adipose tissue biopsy for the in vitro study was taken from subcutaneous abdominal region during the operation. Lipolysis in freshly isolated adipocytes was stimulated with different concentrations of adrenaline or isoprenaline. RESULTS: Significant positive correlations were observed between the values of relative stimulation of lipolysis in isolated adipocytes and in the microdialysis study. These correlations improved after correcting for cell size or fat mass. CONCLUSION: The microdialysis study in vivo and lipolysis assay with isolated adipocytes in vitro provide concordant and complementary information of adipose tissue metabolism in the same individual.

The effect of a very low-calorie diet-induced weight loss on the severity of obstructive sleep apnoea and autonomic nervous function in obese patients with obstructive sleep apnoea syndrome.

The aim of this study was to examine the effect of a very low-calorie diet (VLCD)-induced weight loss on the severity of obstructive sleep apnoea (OSA), blood pressure and cardiac autonomic regulation in obese patients with obstructive sleep apnoea syndrome (OSAS). A total of 15 overweight patients (14 men and one woman, body weight 114 +/- 20 kg, age 52 +/- 9 years, range 39-67 years) with OSAS were studied prospectively. They were advised to follow a 2.51-3.35 MJ (600-800 kcal) diet daily for a 3-month period. In the beginning of the study, the patients underwent nocturnal sleep studies, autonomic function tests and 24-h electrocardiograph (ECG) recording. In addition, 15 age-matched, normal-weight subjects were studied. They underwent the Valsalva test, the deep-breathing test and assessment of heart rate variability at rest. The sleep studies and autonomic function tests were repeated after the weight loss period. There was a significant reduction in weight (114 +/- 20 kg to 105 +/- 21 kg, P < 0.001), the weight loss being 9.2 +/- 4.0 kg (range 2.3-19.5 kg). This was associated with a significant improvement in the oxygen desaturation index (ODI4) during sleep (31 +/- 20-19 +/- 18, P < 0.001). Before the weight loss the OSAS patients had significantly higher blood pressure (150 +/- 18 vs. 134 +/- 20, P < 0.05, for systolic blood pressure, 98 +/- 10 vs. 85 +/- 13, P < 0.05, for diastolic blood pressure) and heart rate (67 +/- 10 beats min-1 vs. 60 +/- 13, P < 0.05) at rest than the control group. They had also lower baroreflex sensitivity (4.7 +/- 2.8 ms mmHg-1 vs. 10.8 +/- 7.1 ms mmHg-1, P < 0.01). During the weight reduction, the blood pressure declined significantly, and the baroreflex sensitivity increased by 49%. In conclusion, our experience shows that weight loss with VLCD is an effective treatment for OSAS. Weight loss improved significantly sleep apnoea and had favourable effects on blood pressure and baroreflex sensitivity that may have prognostic implications.