Scientists solve brain “switch” mystery behind weight loss in possible game changer for obesity drugs

Scientists on the College of Cambridge say they’ve resolved a long-standing puzzle in weight problems analysis: how each activating and blocking the identical mind receptor can cut back meals consumption and physique weight. The examine discovered that the reply lies not merely in whether or not the receptor is switched on or off, however in the place it’s positioned within the mind. The findings have been revealed in Nature Metabolism underneath the title “Distinct mind areas mediate regulation of meals consumption in response to GIPR agonism or antagonism”. The examine was led by Dr Jo Edward Lewis and colleagues on the College of Cambridge’s Institute of Metabolic Science.

The receptor on the centre of this discovery is the glucose-dependent insulinotropic polypeptide receptor (GIPR), which is concerned in regulating urge for food, metabolism and blood sugar. GIPR is a crucial goal within the improvement of weight problems medicines. Medication resembling tirzepatide, offered as Mounjaro and Zepbound, activate GIPR alongside the glucagon-like peptide-1 (GLP-1) receptor. Different experimental medicines take the other strategy by blocking GIPR. MariTide, presently in Section 3 scientific trials, combines GIPR antagonism with GLP-1 receptor activation. The obvious contradiction has puzzled researchers for years. Why ought to each stimulating and blocking the identical receptor contribute to weight reduction?

Cambridge researchers used genetically engineered mice during which GIPR may very well be selectively faraway from explicit areas of the mind. One group lacked GIPR within the brainstem, whereas one other lacked the receptor within the hypothalamus. A management group retained regular GIPR expression. The researchers then examined responses to GIPR agonists and antagonists, in addition to GLP-1 medicines used alone and together. The experiments revealed two distinct mechanisms. When GIPR is activated within the brainstem, it suppresses urge for food, lowering meals consumption and physique weight. Blocking GIPR within the hypothalamus, alternatively, strengthens the mind’s response to indicators indicating that the physique is full.

Within the hypothalamus, GIPR seems to behave as a brake on satiety signalling. Blocking the receptor releases that brake, permitting fullness indicators to grow to be extra highly effective and lowering meals consumption by a special pathway.

The researchers monitored meals consumption, physique weight, fats mass, blood-sugar management and mind exercise all through the examine. Their findings counsel that the identical receptor can affect weight reduction by totally different neural circuits relying on its location within the mind.

The researchers additionally discovered proof that GIPR blockade may improve the consequences of medicines concentrating on the amylin receptor. This raises the opportunity of combining totally different hormone pathways to supply stronger weight-loss results. The findings may assist researchers develop extra exact weight problems remedies that concentrate on particular mind circuits moderately than treating GIPR as a single, uniform swap.

“Understanding which mind circuits reply to those medicines – and the way they achieve this – may assist us design higher medication that produce extra weight reduction with fewer negative effects, and which could work together with different weight problems medicines to even better impact,” Lewis stated.

The examine was funded by the UK Medical Analysis Council and Wellcome. Because the analysis was carried out in mice, the findings don’t but set up that the identical mechanisms will function identically in people. Nevertheless, the work offers a framework for creating the following technology of weight problems medicines and reinforces the central function of the mind in regulating physique weight.