The effects of cystatin C and alkaline phosphatase changes on cognitive function 12-months after bariatric surgery

Abstract

Background The mechanisms for improved cognitive function post-bariatric surgery are not well understood. Markers of kidney and liver function (i.e., cystatin C and alkaline phosphatase (ALP)) are elevated in obese individuals and associated with poor neurocognitive outcomes in other samples. Bariatric surgery can improve cystatin C and ALP levels, but no study has examined whether such changes correspond to post-operative cognitive benefits. Methods 78 bariatric surgery patients completed a computerized cognitive test battery prior to and 12-months after surgery. All participants underwent an eight-hour fasting blood draw to quantify cystatin C and ALP concentrations. Results Cognitive function improved after surgery. Cystatin C levels decreased at the 12-month follow-up; however, no changes were found in ALP concentrations. At baseline, higher cystatin C levels predicted worse attention/executive function, but no such effects emerged for ALP. Regression analyses controlling for possible medical and demographic confounds and baseline factors revealed that decreased ALP levels following surgery predicted better attention/executive function and memory abilities. Post-surgery changes in cystatin C did not correspond to cognitive improvements. Conclusions Decreased ALP levels predicted better cognition following bariatric surgery, suggesting improved liver function as a possible mechanism of post-operative cognitive benefits. Future studies with neuroimaging and longer follow-up periods are needed to determine whether bariatric surgery can decrease risk for adverse brain changes and dementia in severely obese persons via improved metabolic function.

Liver Fibrosis Predicts Cognitive Function Following Bariatric Surgery: A Preliminary Investigation

“…Specifically, patients with liver biopsy demonstrating fibrosis committed more errors on an executive function task (maze test) and recognized fewer words from the verbal list. These findings are consistent with recent work showing that greater postoperative cognitive function is associated with better preoperative liver function measured via ALP in a different sample of bariatric surgery patients (9), and extend past findings by demonstrating that those with greater liver pathology at the time of surgery show poorer postoperative cognitive function than those without. This extension by examination of liver biopsy is important, given recent work showing that blood work of liver function is not a fully reliable estimate of liver health (10).…”

“…The current findings, in the context of past work showing that liver function often improves following bariatric surgery (19) and preoperative ALP is linked to better postoperative cognition (9), suggest a need for future work to determine the extent to which liver function directly affects cognitive abilities. Limitations of the current work include the crosssectional design and single, early postoperative time point, as well as lack of a control group comparison.…”

“…Past work shows that elevated ALP has been linked to poorer cognitive function and Alzheimer's disease . A recent study of bariatric surgery patients demonstrated lower pre‐operative ALP concentrations were linked to better postoperative cognitive function .…”

Changes in Cognitive Function Following Bariatric Surgery: a Systematic Review

“…A smaller sample of 21 patients followed up to 48 months showed significant improvements from baseline Alosco 2014 [62] Postoperative decreases in alkaline phosphatase (ALP) and a lower baseline cystatin C were associated wit bariatric surgery patients followed up at 12 months.…”

Higher Cystatin C Levels Are Associated With Neurocognitive Impairment in Older HIV+ Adults

“…12 Decline in cystatin C levels are also associated with improved cognition after bariatric surgery. 13 Cystatin C levels are elevated in HIV+ adults 14–16 and in the plasma of young HIV+ Hispanic women with NCI. 13 The correlation between cystatin C and neurocognitive function has not yet been investigated, however, in HIV+ older adults.…”