FAT score predicts poor weight loss post-RYGB
Researchers created a fibrosis score of adipose tissue (FAT score) integrating perilobular and pericellular fibrosis and tested its predictive value on weight-loss response after RYGB in 183 perioperative scAT biopsy specimens from severely obese patients (85 from a training cohort and 98 from a confirmation cohort). Mean patient age was 43 years, and average BMI was 47 kg/m2. Seven out of 10 were women, and 39 percent had diabetes.
At 1 year post-RYGB, the FAT score was directly associated with increasing scAT fibrosis (p<0.001). Of note, a FAT score of ≥2 was significantly associated with poor response to RYGB despite adjusting for patient age, diabetes status, high blood pressure, and percentage of body fat (adjusted odds ratio [adjOR], 3.6; p=0.003). Poor response was defined as <28 percent of total weight loss at 1-year post-surgery. Poor responders lost an average 22.7 percent of body weight whereas good responders lost 35.6 percent. This translates to an average difference of 17 kg in weight loss between groups. [EASD 2017, abstract OP-32; J Clin Endocrinol Metab 2017;102:2443–2453]
“The most severe fibrosis scores [greater than 2] presurgery were associated with a poorer weight-loss response of 3–4 times the risk,” said lead investigator Dr Pierre Bel Lassen from INSERM and Pitié-Salpêtrière Hospital, Assistance Publique– Hôpitaux de Paris in Paris, France.
Factors predicting poor response to RYGB include older age, diabetes, hypertension, and eating disorders, he said. “[However,] if we pool these presurgery factors, it can only detect 14 percent of post-bariatric weight loss.”
Color detection of collagen in the adipose tissue can also predict weight loss after surgery, but the procedure is time-consuming, depends on slide quality, and is affected by heterogeneity of fibrosis, he added. “We need a novel, easy-to-use score that would be reproducible in the clinic to predict outcomes in these patients.”
The FAT score was a significant improvement of previous attempts to determine surgical outcomes. However, it can only predict responses in 72 percent of patients, Bel Lassen acknowledged. “Further refinement is therefore needed, possibly by including other biological or psychological factors that are absent from the current model.”
Bel Lassen’s team would also like to expand their study to determine if the FAT score can be applied to other types of bariatric surgery such as sleeve gastrectomy, and determine its predictive value over longer follow-up periods.
Commenting on the study, Dr Jan Eriksson, an endocrinologist from Uppsala University in Uppsala, Sweden, who is unaffiliated with the study, said the work had value in finding a measure that could predict who would benefit from RYGB, but it is also interesting from a pathobiology perspective. “It is surprising that there was an increase in the fibrosis score following the procedure … I would have expected the opposite, and this needs further research.”