Miriam E Tucker

September 25, 2017

LISBON, PORTUGAL — Roux-en-Y gastric bypass (RYGB) surgery reduces the risk for retinopathy in obese patients with type 2 diabetes, whether or not they experience diabetes remission following the operation, new research indicates.

Findings from the two-phase study of 96 operated and 48 nonoperated matched obese type 2 diabetes patients were presented September 13 here at the European Association for the Study of Diabetes (EASD) 2017 Annual Meeting by Lene Ring Madsen, MD, of the department of endocrinology and internal medicine, Aarhus University, Denmark.

In a 6-year follow-up, the patients who had undergone RYGB surgery had a 60% greater chance of unchanged or better diabetic retinopathy than did the controls, regardless of diabetes-remission status.

"What you can learn from my study is that it does not seem harmful on diabetic retinopathy to do a Roux-en-Y gastric bypass in people with type 2 diabetes. They might even do better than those who do not get the surgery," Dr Madsen told Medscape Medical News. However, she added, "my cohort is highly selected," since they had a presurgical body mass index of greater than 48 kg/m2.

Session moderator Massimo Porta, professor of internal medicine, University of Turin, Italy, said that although the findings weren't completely surprising, they provide confirmation: "This is one of the first papers to show that improved metabolic control [via surgery] is linked to arrest of progression of diabetic retinopathy."

However, he added, "I don't know if you can base the decision for surgery only on that, but certainly it's an additional piece of information."

Two-Part Study Shows Long-term Benefit

Several previous trials show that RYGB surgery induces diabetes remission in some patients and that the resultant improved glycemic control over time reduces diabetic retinopathy progression.

But some studies have also linked rapid improvements in blood glucose with short-term worsening of diabetic retinopathy.

The 96 patients in the current study had a mean baseline body-mass index 47.8 kg/m2 and were matched with the 48 nonoperated controls with type 2 diabetes for age, gender, and current BMI. Diabetes remission, defined as an HbA1c below 6.5% with no glucose-lowering medications, occurred following surgery in 48 of the operated patients.

In an initial cross-sectional study phase, with a mean of 6.1 years after surgery, just 2% of the operated group with remission had severe retinopathy (grades 3–6), vs 19% of those without remission after surgery and 10% of the nonoperated control patients (< .001) while 87.5%, 52%, and 77%, respectively, had no retinopathy (grade 1).

After adjustment for diabetes duration, gender, and smoking status, the relative risks for any diabetic retinopathy were 0.36 for the remission group vs controls and 0.75 for the nonremission group vs controls, both significant. In contrast, the difference between the remission and nonremission groups was not significant.

In a 6-year follow-up phase, conducted in a subgroup of 65 patients for whom presurgical fundus photos were available (23 remission, 26 nonremission, and 16 controls), both RYGB with diabetes remission and RYGB without remission displayed a reduced grading from first to second retinal photo imaging (-0.19 [= .011] and -0.04 [= .001]) compared with controls, who experienced significant worsening (+0.69).

Relative risks for better or unchanged retinopathy, adjusted for diabetes duration and severity of first grading, were 1.60 for remission vs controls and 1.63 for nonremission vs controls (both significant), while there was no difference in the remission vs nonremission groups (0.98).

A Second Study Adds Support

In a separate study presented as a poster at the EASD meeting, Dr Robyn J Tapp, of Leeds Beckett University, United Kingdom, and colleagues examined the effect of bariatric surgery — either RYGB or sleeve gastrectomy — on 22 obese females (mean BMI, 40.8 kg/m2) on the retinal microvasculature, with ophthalmic examinations at baseline and again at 6 months postsurgery. Diabetes status wasn't reported, but they had a mean baseline fasting glucose of just 5.4 mmol/L (97 mg/dL).

After surgery, the central retinal artery equivalent increased from baseline to 6 months (= .013) while the central retinal vein equivalent decreased (= .046), whereas no changes in either measure occurred in a group of 15 lean female age-matched controls (= 0.22 and 0.550, respectively).

The arteriolar-to-venular ratio also increased following bariatric surgery (= .002), with no changes among the controls (= .550).

"The findings suggest obesity-related microvascular changes are reversible after bariatric-induced weight loss. The capacity for the retinal microvasculature to improve following bariatric surgery suggests plasticity of the human microvasculature early in the disease course," Dr Tapp and colleagues conclude.

But, Dr Porta noted, it's important to consider the downsides: "Of course, there are the caveats of surgery.…I'm always very prudent and cautious before I suggest patients go into that kind of surgery. I always try everything else first."

Dr Madsen has no relevant financial relationships. Dr Porta consults for or is an advisor to Abbott, Allergen, Novartis, Novo Nordisk, and Sanofi.

European Association for the Study of Diabetes (EASD) 2016 Annual Meeting. September 13, 2017, Lisbon, Portugal. Abstract 119, Abstract 1047

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