Lifestyle leading to overweight increases the risk of metabolic diseases such as diabetes – but the relationship also works in reverse, according to a new study. If insulin production is compromised, as is the case in the early stages of type 2 diabetes, this can contribute to overweight. The researchers report their findings in the journal Nature Communications.
When hormone activation goes awry
The research group, led by Dr Daniel Zeman-Meier of the University Hospital of Basel, focused on protease PC1/3 – a key enzyme in the body that transforms various inactive hormone precursors into the final, active forms. Sever endocrine disorders can result if PC1/3 does not function properly. The consequences include a feeling of uncontrollable hunger and severe overweight.
“Until now, it was assumed that this dysregulation is caused by a lack of activation of satiety hormones,” explained Dr Zeman-Meier. “But when we turned off PC1/3 in the brains of mice, the animals’ body weight did not change significantly.” The researchers concluded from this that something other than a brain malfunction must be responsible.
Incorrect activation of insulin leads to hunger and overweight
In their next step, they tested whether overweight could be caused by incorrect activation of other hormones. Among other things, PC1/3 activates insulin. “Investigating the role of insulin production as a cause of overweight was obvious,” said Dr Zeman-Meier. The researchers shut off PC1/3 specifically in the insulin-producing beta cells of the pancreas in mice. The animals consumed significantly more calories and soon became overweight and diabetic.
An important mechanism in humans
“These results are also interesting because PC1/3 is reduced in the pancreas of patients with prediabetes,” says Professor Marc Donath, research leader and final author of the study. This indicates that incorrect insulin activation could cause overweight as well as result from it.
But PC1/3 is also important in the weight regulation of healthy individuals, Prof Donath stressed. The researchers were able to show that the gene expression of PC1/3 in the pancreas is negatively correlated with body weight in the general population — meaning that sufficient PC1/3 promotes a healthy body weight.
The finding that a defect in the beta cells is a trigger of overweight promises new therapeutic possibilities. For example, it is conceivable that medications could be used to reduce the production of immature insulin precursors, creating a new tool in the fight against overweight and diabetes.
Source: University of Basel
