Low levels of a specific hormone has been found to increase the risk of metabolic disease in humans, according to a study.
The study focuses on the hormone adropin, which is believed to play an important role in regulating glucose levels and fatty acid metabolism.
The hormone was previously identified by Scripps Research Associate Professor Andrew Butler's laboratory during an investigation of obese and insulin-resistant mice.
"The results of this clinical study suggest that low levels of adropin may be a factor increasing risk for developing metabolic disorders associated with obesity and insulin resistance, which could then lead to diseases such as type 2 diabetes," said Butler, who led the new study with Peter J. Havel, professor of molecular biosciences and nutrition at the University of California, Davis.
The National Institutes of Health defines metabolic syndrome as a group of risk factors, especially obesity and insulin resistance, that occur together and increase the risk for coronary artery disease, stroke, and type 2 diabetes.
In the new study, which involved 85 women and 45 men, Butler and his colleagues showed that obesity is associated with lower adropin levels. Lower adropin levels were also observed in individuals with a higher "metabolic syndrome risk factor" score, a score determined by measuring triglycerides, LDL cholesterol, HDL, glucose, blood pressure, and waist circumference.
The scientists also observed circulating adropin concentrations increased significantly at three and six months following gastric bypass surgery in morbidly obese patients. Interestingly, adropin levels returned to pre-surgical levels at 12 months after surgery.
Another surprising finding of the new study was that in people of normal weight, women had lower plasma adropin levels than men. In addition, obesity had a bigger negative effect on adropin levels in men. Interestingly, obesity in woman was also not associated with lower plasma adropin levels. The significance of the differences between men and woman is unknown at the moment.
"But the link between low levels of adropin and increased metabolic risk was observed in both sexes," Butler said. "The impact is there, irrespective of gender."
Adropin levels were also found in general to decrease with age-the decline was highest in those over 30 years of age. As with obesity, the aging effect appeared to be more pronounced in men.
Taken together, these results suggest the possibility that therapeutics designed to boost the supply of adropin might be useful in fighting obesity and metabolic disease.
The results have been published online ahead of print in The Journal of Clinical Endocrinology and Metabolism.