Improvements in Diabetic Neuropathy and Nephropathy After Bariatric Surgery: a Prospective Cohort Study

Abstract Purpose There are limited data on the impact of bariatric surgery on microvascular complications of type 2 diabetes (T2D), particularly diabetic neuropathy. We assessed microvascular complications (especially neuropathy) in obese patients with T2D before and 12 months after bariatric surgery. Materials and Methods This was a prospective observational cohort study. Measurements of neuropathy symptom profile (NSP), neuropathy disability score (NDS), vibration (VPT), cold (CPT) and warm (WPT) perception thresholds, nerve conduction studies (NCS) and corneal confocal microscopy (CCM) to quantify corneal nerve fibre density (CNFD), branch density (CNBD) and fibre length (CNFL); urinary albumin/creatinine ratio (uACR), estimated glomerular filtration rate (eGFRcyst-creat) and retinal grading were taken. Results Twenty-six (62% female; median age 52 years) obese patients with T2D were recruited. Body mass index (BMI) (47.2 to 34.5 kg/m 2 ; p < 0.001) decreased post-operatively. There were improvements in CNFD (27.1 to 29.2/mm 2 ; p = 0.005), CNBD (63.4 to 77.8/mm 2 ; p = 0.008), CNFL (20.0 to 20.2/mm 2 ; p = 0.001), NSP (3 to 0/38; p < 0.001) and eGFRcyst-creat (128 to 120 ml/min; p = 0.015) post-bariatric surgery. Changes in (Δ) triglycerides were independently associated with ΔCNFL ( β = − 0.53; p = 0.024) and Δsystolic blood pressure (β = 0.62; p = 0.017), and %excess BMI loss ( β = − 0.004; p = 0.018) were associated with ΔeGFRcyst-creat. There was no significant change in NDS, VPT, CPT, WPT, NCS, uACR or retinopathy status. Glomerular hyperfiltration resolved in 42% of the 12 patients with this condition pre-operatively. Conclusion Bariatric surgery results in improvements in small nerve fibres and glomerular hyperfiltration in obese people with T2D, which were associated with weight loss, triglycerides and systolic blood pressure, but with no change in retinopathy or uACR at 12 months.