As shown in Table 2, fasting glucose and HbA1c decreased significantly in the RYGB group. In the limited subset of subjects (N = 9) who had fasting insulin available, fasting insulin changed by −22 μU/mL (−31 to −11, P = 0.003), and homeostatic model assessment-insulin resistance (HOMA-IR) changed by −4.7 (−7.0 to −2.3, P = 0.004). In the 2 patients who had type 2 diabetes mellitus (T2DM) before surgery, diabetes was noted to be resolved at follow-up. Total cholesterol, low-density lipoprotein, and triglycerides also significantly decreased (Table 2).
In the RYGB group as a whole, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) did not significantly change following surgery (Table 2). Among the subgroup (N = 6) of patients who had elevated ALT or AST at baseline, however, RYGB resulted in a significant decline in AST (−12 U/L [−23 to −3], P = 0.03) and ALT (−27 U/L [−46 to −11], P = 0.03). Serum creatinine showed a small but significant decrease following RYGB (Table 2, P = 0.03).
High-sensitivity C-reactive protein (hsCRP) changed by −6 mg/L (−13 to −2) following RYGB (P = 0.0007). Although sample size was limited, the decrease in CRP in girls was greater than in boys (P = 0.03). Sedimentation rate changed by −9 mm/h (−18 to −6) in the RYGB group during follow-up (P = 0.0001). White blood cell count (−2.2 cells/mm3 [−4.0 to −0.8], P = 0.001) and platelet count (−41 cells/mm3 [−81 to −2], P = 0.004) also decreased. In univariate analysis within the RYGB group, age at surgery was not associated with changes in weight or changes in metabolic variables. Of note, postsurgical changes in body weight were not significantly associated with changes in fasting glucose, HbA1c, lipid, or systemic inflammatory markers (hsCRP, erythrocyte sedimentation rate [ESR]); P > 0.2 for all.
Changes in controls during the follow-up period are shown in Table 2. The control group did not experience significant weight loss during the follow-up period, and, compared with controls, the %EBMIL in the RYGB group was highly significant (P < 0.0001). Changes in fasting glucose (P = 0.02) and HbA1c (P = 0.02) were also significant in RYGB versus controls. There were not sufficient data in controls to compare changes in fasting insulin or HOMA-IR. The decrease in low-density lipoprotein after RYGB was significant (P = 0.03) compared with controls, whereas the change in triglycerides was not significant (P = 0.4). Declines in white blood cell count (P = 0.002) and platelets (P = 0.003) were significant in RYGB versus controls, whereas there were not sufficient control data to compare changes in hsCRP or ESR. There was a small decrease in creatinine in the RYGB group that just reached statistical significance as compared with controls (P = 0.05).
Our data demonstrate improvements in multiple metabolic parameters following RYGB in adolescents and young adults, many of which were highly significant compared with controls. Age was not significantly associated with outcomes. Moreover, the magnitude of metabolic improvement was not significantly associated with the degree of weight loss, supporting recent research that RYGB alters critical endocrine and metabolic pathways independent of caloric restriction and weight loss (6–8); however, our small sample size may have limited our ability to detect associations between magnitude of weight loss and improvement in metabolic variables.
As shown in previous studies in adolescents, glucose homeostasis improved in our cohort following RYGB (9,10). In the 2 of 24 RYGB subjects who had T2DM at baseline, T2DM resolved postsurgically, consistent with previous reports in adolescents and adults (10). Although the majority of our cohort was nondiabetic, significant improvements were seen in HbA1c (−0.4%), fasting glucose (−9 mg/dL), insulin (−22 μU/mL), and HOMA-IR (−4.7). The magnitude of these changes is similar to changes reported in other RYGB cohorts (9,11).
Markers of chronic inflammation, including CRP and ESR, decreased significantly in RYGB subjects. Reduction in CRP has been reported in adult WLS cohorts (12,13), but to our knowledge this is the first report of reductions in hsCRP and ESR in adolescents and young adults following RYGB. We also noted reductions in leukocyte and platelet counts after RYGB. Before the widespread use of hsCRP as a marker of inflammation, population studies showed strong positive associations between leukocyte count and future cardiovascular disease risk (14,15). Thrombocytosis is also associated with systemic inflammation (16) and obesity (17), and relatively higher platelet counts predict future cardiovascular disease (18). To our knowledge, the small but significant decrease in serum creatinine after RYGB has not yet been reported in adolescents and young adults but is consistent with data in adults showing a 0.1-mg/dL decrease in creatinine 6 months after RYGB (19).
There are important limitations to the present study. This was a retrospective study dependent on clinical data, which were not consistently collected in all patients. RYGB patients and controls were matched only on the basis of sex, age, and BMI, and we were not able to match on other potentially important factors such as earlier weight history and follow-up interval. Height and weight were collected by multiple clinical staff rather than a single evaluator. In addition, we have a relatively small sample size and limited time frame for evaluation of postoperative changes. More important, previous studies have shown a modest decline in success rates 2 to 3 years postoperatively in patients after gastric bypass, and it will be necessary to follow adolescents undergoing RYGB further to assess this issue; however, given the relatively limited data on outcomes of WLS in adolescents and young adults, we believe our data, in combination with reports from other relatively small cohorts, contribute to our knowledge of metabolic outcomes of RYGB in this age group. Consistent with other studies, we demonstrate significant improvements in glucose homeostasis and lipid measures, and, for the first time in this age group, we show significant changes in markers of inflammation, including CRP, as well as improvements in creatinine. Further studies are necessary to elucidate the mechanisms of these changes.
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Keywords:© 2013 by European Society for Pediatric Gastroenterology, Hepatology, and Nutrition and North American Society for Pediatric Gastroenterology,
adolescence; glucose; high-sensitivity C-reactive protein; obesity; roux-en-Y gastric bypass