Bariatric surgery´s effects on diabetic neuropathy
Could bariatric surgery revert diabetic neuropathy? Some suggests it could (Adam, 2021).
Bariatric surgery for obesity
As obesity rates are rising, so is bariatric surgery´s popularity. In 2019, more than 250,000 bariatric weight loss surgeries have been reported in the United States alone. (Estimate of Bariatric Surgery Numbers, 2011-2019, 2021)
Besides weight loss, this treatment promotes long-term benefits such as remission from Type 2 Diabetes (T2D), and decrease in incidence of macrovascular events (Adam, 2021).
However, only few studies analyzed one of the early microvascular outcomes: neuropathy.
To fill this gap, Adam et al. assessed the effects of bariatric surgery over 12 months on microvascular complications, specifically neuropathy, in a cohort of obese patients with T2D (Adam, 2021).
This study analyzed 26 obese patients with T2D before, and 12 months after bariatric surgery.
Assessments included body mass index (BMI), excess BMI loss (%EBMIL), blood pressure, and estimated glomerular filtration rate (eGFR). The participants also provided blood and early morning urine samples for biochemical analysis.
The Neuropathy Symptom Profile Questionnaire evaluated sensory, motor, and autonomic neuropathy symptoms. Additionally, researchers assessed temperature and vibration sensation, and ankle reflexes to calculate the Neuropathy Disability Score. Small fiber corneal morphology was assessed using Corneal Confocal Microscopy (CCM).
Cold and warm thermal thresholds were assessed using Medoc´s TSA-II NeuroSensory Analyser on the S1 dermatome of the left foot.
Bariatric surgery successfully reduced the patients’ BMI at 12 months. The mean %EBMIL was 61±16%.
About 80% of the patients enjoyed a complete remission in T2D. Blood pressure and HbA1C significantly decreased. High-density cholesterol levels also increased.
Six out of 26 participants had diabetic neuropathy at baseline as assed by the Neuropathy Disability Score. Somatosensory alterations in obesity have also been reported by other studies where obese patients seem to have altered thermal thresholds. For instance, Iqbal et al. showed that obese patients had higher warm detection thresholds, than normal weight individuals. (Iqbal, 2021)
There was a significant improvement in the Neuropathy Symptom Profile Questionnaire 12 months after bariatric surgery. There were also improvements in corneal nerve fiber density, nerve branch density, and nerve fiber length. However, there was no change in vibration, cold, or warm perception, as measured by quantitative sensory testing (QST), nor was there improvement in retinopathy.
Reversal of Diabetes and neuropathy?
Adam et al. showed the major benefit of bariatric surgery; weight loss and reversal of T2D. In this study, subjective reports by the patients regarding signs of neuropathy seem promising of bariatric surgery’s potential in reversing neuropathy. However, these reports were not substantiated by changes in QST. (Adam, 2021) Likewise, Azmi et al. showed an improvement in neuropathy symptoms and disability, but no change in cold and warm thresholds 12 months after bariatric surgery. The authors in that study argued that the lack of changes in QST might reflect a need for a longer follow-up. (Azmi, 2021) Similarly, (Iqbal, 2021) did not find any change in thermal thresholds one year after bariatric surgery of obese patients. In contrast to (Adam, 2021) and (Azmi, 2021), Iqbal et al. did not find changes in patient reported neuropathy complaints like the neuropathy disability score, or the neuropathy symptoms profile.
Interestingly, in neither of the mentioned studies, had the patients reached normal weight (BMI between 18.5-24.9 kg/m2) (Healthy Weight Nutrition and Physical Activity - Assessing your Weight, 2020) at 12 months' follow-up. A longer follow-up of these patients into the realms of normal weight might show different results in terms of thermal thresholds.
Adam, S. A. (2021). Improvements in diabetic neuropathy and nephropathy after bariatric surgery: a prospective cohort study. Obesity surgery, 554-563.
Azmi, S. F. (2021). Bariatric surgery leads to an improvement in small nerve fibre damage in subjects with obesity. International Journal of Obesity, 631-638.
Estimate of Bariatric Surgery Numbers, 2011-2019. (2021, March). Retrieved from The American Society for Bariatric and Metabolic Surgeries: https://asmbs.org/resources/estimate-of-bariatric-surgery-numbers
Healthy Weight Nutrition and Physical Activity-Assessing your Weight. (2020, September). Retrieved from Centers for Disease Control and Prevention: https://www.cdc.gov/healthyweight/assessing/index.html
Iqbal, Z.K. (2021). Corneal keratocyte density and corneal nerves are reduced in patients with severe obesity and improve after bariatric surgery. Investigative ophthalmology, 1-8.