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Insulin sensitivity and surgery

Insulin sensitivity improves following RYGB surgery

Credit: Alden Chadwick/Flickr
The results showed improvements in peripheral insulin sensitivity mainly occurred at 12 monoths post-surgery when major weight loss was evident and occurred concomitantly with alterations in plasma adiponectin and in protein expression/ signalling

Roux-en-Y gastric bypass (RYGB) can lead to remission of type 2 diabetes along with weight loss, according to a study ‘Enhanced insulin signaling in human skeletal muscle and adipose tissue following gastric bypass surgery.’, in the American Journal of Physiology—Regulatory, Integrative and Comparative Physiology, that investigated the effect of RYGB on expression and regulation of proteins involved in regulation of peripheral glucose metabolism.

Insulin is the primary hormone responsible for transferring glucose into the body's tissues to be used by the cells or stored, and the skeletal muscles and fat tissues are the main glucose storage sites in the body. How readily the body responds to insulin, (insulin sensitivity), indicates how quickly glucose can be transferred out of the blood. Poor insulin sensitivity slows the uptake of glucose into the skeletal muscle and fat tissues and leads to a high blood sugar level. Decreased insulin sensitivity is common in people with obesity and type 2 diabetes.

The researchers took skeletal muscle and adipose tissue biopsies from obese patients with type 2 diabetes and obese patients with normal glucose control before (one week) and after (three and 12 months) gastric bypass surgery.

The results showed improvements in peripheral insulin sensitivity mainly occurred at 12 monoths post-surgery when major weight loss was evident and occurred concomitantly with alterations in plasma adiponectin and in protein expression/signalling in peripheral tissues. In skeletal muscle, protein expression of GLUT4, phosphorylated levels of TBC1D4, as well as insulin-induced changes in phosphorylation of Akt and glycogen synthase activity were enhanced 12 months post-surgery.

In adipose tissue, protein expression of GLUT4, Akt2, TBC1D4, and acetyl-CoA carboxylase (ACC), phosphorylated levels of AMP-activated protein kinase and ACC, as well as insulin-induced changes in phosphorylation of Akt and TBC1D4, were enhanced 12 mo postsurgery. Adipose tissue from glucose-tolerant subjects was the most responsive to RYGB compared with type 2 diabetic patients, whereas changes in skeletal muscle were largely similar in these two groups.

The researchers said that the data suggest that improved insulin sensitivity in the skeletal muscle and fat tissue contribute to the improved whole-body insulin action following gastric bypass surgery. These adaptations were observed only after significant weight loss had occurred, the research team noted.

Interestingly, improvement in insulin sensitivity was associated with changes in fat tissue rather than skeletal muscle, suggesting that fat tissue may play a larger role in insulin sensitivity than currently believed, they added.

“An improved molecular insulin-sensitive phenotype of skeletal muscle and adipose tissue appears to contribute to the improved whole body insulin action following RYGB. These adaptations are seen in both obese NGT and T2D subjects after a significant weight loss only. Of notice, changes in the adipose tissue, rather than skeletal muscle, are associated with the changes in insulin sensitivity,” they concluded. “Our study suggests novel adaptations in the interplay between insulin and AMPK signalling with RYGB/weight loss that could contribute to a more insulin-sensitive and metabolically flexible adipose tissue.”

The study was performed by researchers from the University of Copenhagen in collaboration with Novo Nordisk A/S, Hvidovre Hospital and Aarhus University in Denmark.

To access this paper, please click here or as a pdf here

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