The main findings in this study were that liver enzymes, GGT and ALT, markedly decreased over time after both RYGBP and BPD-DS surgeries, but platelet counts only decreased significantly after BPD-DS. The alteration in platelet counts showed a somewhat different pattern after RYGBP, with a reduction at the 1st followup but no significant change at the 2nd followup. It might be speculated that the sustained reduction in platelet counts may indicate a long-term improvement in the inflammation of the liver and a more pronounced decrease of liver-fat-content-related inflammation in obese patients treated by BPD-DS compared to RYGBP. Platelets vary daily and are depending on a variety of issues such as ethnicity, age, and gender. However, longitudinal studies demonstrate considerable stability of steady-state platelet counts. Buckley et al. have showed in their analysis of serial platelet counts from 3,789 subjects that the repeatability of the platelet count is very high [22
]. Obesity is an inflammatory condition [23
] and a major risk factor for the development of NAFLD and liver disease. In obese patients, ultrasonographic examinations as well as liver biopsies have revealed that NAFLD is very common [17
]. As it is difficult to perform biopsies in all NAFLD patients, biomarkers are warranted to predict prognosis and to optimize treatments. It has been reported that a lowered GGT may best predict improvements in inflammation and fibrosis in the hepatocytes in NAFLD, which are two major prognostic features in this condition, whereas changes in aminotransferase concentrations did not predict change in steatosis [11
]. Furthermore, increased numbers of platelets are observed in conditions with low-grade inflammation, such as obesity, although the platelet counts are within normal ranges [25
]. Overweight, obese, and morbidly obese females have significantly elevated platelet counts compared with normal-weight females and male subgroups [25
]. The gender difference in platelets might be due to the higher body fat mass in females. Higher platelet counts are associated with more adverse clinical outcomes in patients with myocardial infarction and stroke [25
]. Obesity is also associated with platelet dysfunction, increased adhesiveness, and activation [26
]. In more severe states of NAFLD with fibrosis, a consumption of thrombocytes are observed [29
]. In a recent study, Yoneda et al. used liver biopsies to evaluate the clinical usefulness of measuring platelet counts for predicting the severity of liver fibrosis in 1,048 patients with NAFLD [16
]. They suggest platelet count to be a major “ideal” biomarker. Bariatric surgery reverses or improves NAFLD in many cases. There is a lack of data on platelet count changes after BPD-DS. Our data show a sustained reduction in platelet counts over time after BPD-DS, probably induced by a more pronounced weight loss than after RYGBP and possibly a more pronounced decrease of liver inflammation. One year after RYGBP, a significant reduction in platelet counts was observed, which is in accordance with 1 year data from Dallal et al. [14
], but the reduction was not sustained at the 2nd followup, 3 years after surgery.
There are several limitations in the present study such as the small number of patients and the lack of a morbidly obese control group followedup over 3 years. However, such patients can be logistically difficult to follow for long term followups. The BPD-DS group was significantly younger than the RYGBP group, but no differences were observed between the two groups at baseline in platelet counts, GGT or ALT. Body fat content and liver fat content, measured by imaging techniques such as dual energy X-ray absorptiometry or ultrasonography, would have been warranted to investigate if and how different fat distribution might influence the variables analyzed in this study.
In conclusion, morbidly obese patients treated with RYGBP and BPD-DS show a marked and sustained decrease in GGT and ALT. A significant reduction in platelets, a marker for inflammation and fibrosis in NAFLD, was observed in both groups after 1 year but only in BPD-DS over time, which may indicate improvements in general inflammatory status and particularly steatohepatitis. However, extended studies are needed to confirm our findings.