The review’s findings are shared in the latest edition of Obesity, in which the hormone, adropin appears to be sensitive to dietary macronutrients, with carbohydrate-rich diets suppressing circulating levels.
In mice studies, adropin has been strongly linked to lipid metabolism and subsequently metabolic conditions such as cardiovascular disease and type 2 diabetes (T2D). However, the hormone’s function in humans is still uncertain.
Additional results revealed that subjects with low levels of adropin had a higher percentage of fat circulating in the blood.
Low levels of this hormone were also linked to elevated levels of LDL (bad) cholesterol and triglycerides establishing an association with an increased risk of heart disease.
Combo of three studies
Researchers from Saint Louis University gathered data from three studies. The Caloric Restriction, Exercise, and Glucoregulation in Humans (CREG) study, involved sedentary men and women with excess weight aged 45 to 65 years.
They were assigned to groups with the goal of achieving a weight loss of 6 to 8%. Methods used included calorie restriction (CR), endurance exercise training (EX), or a combination (CREX).
Food diaries were also used for 3 days before starting weight loss intervention in order to monitor nutrient intake.
Similarly, the mixed-meal tolerance (MMTT) study, also enrolled sedentary weight-stable individuals (2 males, 7 females) aged 48 to 67 years who were overweight or obese and diagnosed with T2D.
Here, adropin concentrations were compared before (pre) and after (post) a 7-day exercise intervention. After an overnight fast, blood samples were taken and subjects then consumed around 400 kcal in a mixed meal containing 60% energy as carbohydrates (2/3 as simple sugars).
The final study, a meta-analysis to determine normal plasma adropin concentrations, used data obtained from samples obtained from studies performed at the University of Missouri-Columbia.
“This study shows that the levels of adropin in blood correlate with carbohydrate intake. Higher habitual intake of carbs is associated with lower levels of adropin,” said Andrew Butler, professor of pharmacology and physiology at Saint Louis University.
“Conversely, a proportionately higher intake of fat may be associated with higher levels of adropin. It may be that habitual consumption of carbohydrate-rich diet suppresses circulating levels of adropin.”
Discussing the data
Discussing the results, the researchers speculated as to the effect a high-carbohydrate breakfast would have on plasma adropin values.
“While speculative, if plasma adropin values are an indicator of long-term food selection preferences, then a supervised change in feeding behaviour could have a greater impact on plasma adropin concentrations compared with someone who regularly consumes carbohydrate-rich diets,” the study noted.
Less clear was the regulation of plasma adropin concentrations by sugars in humans. Glucose intake, as 25% of daily energy requirements for two to 10 weeks, reduced plasma adropin concentration.
Meanwhile, fructose intake, as 25% of daily energy requirements, had been noted as having an opposite effect. Plasma adropin concentrations in humans may be affected by multiple factors, including diet composition and secondary effects of diet on metabolic condition.
"This study is just a snapshot and it says that there is a link with diet," added Butler. "It further implies that adropin may have a role in maintaining healthy metabolic control."
The study was funded by Novo Nordisk's Diabetes Innovation Award Program, the Lottie Caroline Hardy Charitable Trust, the National Institutes of Health, University of California and University of Missouri Research Council.
Published online ahead of print, DOI: 10.1002/oby.21557
“Inverse association between carbohydrate consumption and plasma adropin concentrations in humans.”
Authors: Andrew Butler et al.