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Genetics

Metabolic improvements after bariatric surgery

Data are descriptive and only show an association
The researchers claim their findings warrant further functional studies

A new study has concluded that Munc18c gene expression is associated with short-term metabolic improvement after bariatric surgery.

According to the study published online published in the journal Plos One, Munc18c gene expression in human adipose tissue is down-regulated in morbid obesity and insulin may have an effect on the Munc18c expression.

“A new finding of this study is the inverse association between Munc18c gene expression in adipose tissue and many clinical variables associated with a poorly metabolic profile, such as weight, BMI, and waist and hip circumferences,” the authors write.

It is known that Munc18c is associated with glucose metabolism and could play a relevant role in obesity. However, little is known about the regulation of Munc18c expression.

As a result, researchers Instituto de Salud Carlos III, Tarragona and the Hospital Regional Universitario Carlos Haya, Malaga, Spain analysed Munc18c gene expression in VAT and SAT in 70 patients (12 non-obese, 23 overweight, 12 obese and 23 non-diabetic morbidly obese patients - 11 with low insulin resistance and 12 with high insulin resistance).

All the morbidly obese patients underwent biliopancreatic diversion (BPD) of Scopinaro, and were also studied 15 days after bariatric surgery. The non-morbidly obese patients underwent laparoscopic surgery for hiatus hernia or cholelithiasis, with no alterations in lipid or glucose metabolism, and with a similar age and with the same selection criteria as those for the morbidly obese group.

Blood samples from all subjects were collected after a 12-hour fast. Serum glucose, cholesterol, high density lipoprotein (HDL) cholesterol and triglycerides were measured by standard enzymatic methods.

Visceral and subcutaneous adipose tissues were obtained during bariatric surgery in the morbidly obese patients and during laparoscopic surgery in the non-morbidly obese patients.

Results

They report that the lean, overweight and obese persons had a greater Munc18c gene expression in adipose tissue than the morbidly obese patients (p<0.001). VAT Munc18c gene expression was predicted by the body mass index (p=0.009). In SAT, no associations were found by different multiple regression analysis models.

In order to strengthen the independence of these associations as predictors of Munc18c gene expression, a multiple regression analysis model was constructed for each depot. In the VAT depot model, sex, age, BMI, waist and hip circumferences and adiponectin were selected as independent variables.

In addition, SAT Munc18c gene expression was the main determinant of the improvement in the HOMA-IR index 15 days after bariatric surgery (p=0.038), whilst SAT explant cultures showed that insulin produced a significant down-regulation of Munc18c gene expression (p=0.048).

“The results show that Munc18c gene expression in human VAT and SAT were down-regulated in morbidly obese patients”, they note. “However, human data are very scarce regarding adipose tissue expression. Also, SAT Munc18c gene expression was inversely associated with insulin. Moreover, insulin down-regulated the Munc18c gene expression in SAT culture.”

This study is the first to report the effects of insulin on SAT Munc18c gene expression in an in vitro model, and the researchers claim their findings warrant further functional studies to show the precise mechanism involved in the regulation of Munc18c gene expression.

“We found that Munc18c gene expression was associated with the short-term metabolic improvement after bariatric surgery,” they conclude. “However, the data reported in this study are only descriptive and only show an association.”

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