GLP\u20111 receptor agonists are among the success stories of modern diabetes care. They lower HbA1c, support weight loss, and\u2014depending on the specific drug and the patient\u2019s risk profile\u2014offer addi\u00adtional cardio\u00adme\u00adta\u00adbolic bene\u00adfits. Nevert\u00adheless, a fami\u00adliar pheno\u00admenon persists in prac\u00adtice: Some pati\u00adents respond less well than expected, even though the admi\u00adnis\u00adtra\u00adtion, dose, and dura\u00adtion of therapy are correct.<\/p>\n
A recent study in Genome Medi\u00adcine provides a possible genetic expl\u00adana\u00adtion for this. The focus is on the PAM gene, which encodes peptidyl-glycine alpha-amida\u00adting monooxygenase.<\/p>\n
This enzyme is involved in the amida\u00adtion of nume\u00adrous bioac\u00adtive peptides\u2014including GLP\u20111. Two hypo\u00admor\u00adphic PAM vari\u00adants studied, p.S539W and p.D563G, are asso\u00adciated with an increased risk of type 2 diabetes; combined, they are carried by about one in ten people.<\/p>\n
More GLP\u20111 does not mean increased effectiveness<\/b><\/p>\n
In the study, PAM acti\u00advity was signi\u00adfi\u00adcantly reduced in carriers of these vari\u00adants: by about 52% for p.S539W and by about 20% for p.D563G.<\/p>\n
Inte\u00adres\u00adt\u00adingly, carriers also had elevated circu\u00adla\u00adting GLP\u20111 levels. While this may initi\u00adally sound like an advan\u00adtage, it does not trans\u00adlate into a stronger effect. Reduced endo\u00adge\u00adnous GLP\u20111 sensi\u00adti\u00advity was parti\u00adcu\u00adlarly evident with p.S539W\u2014consistent with the concept of GLP\u20111 resistance.<\/p>\n
The mouse data also fit this picture: Pam knockout mice exhi\u00adbited acce\u00adle\u00adrated gastric emptying, responded less well to exendin\u20114, and showed atte\u00adnu\u00adated signal trans\u00adduc\u00adtion via the GLP\u20111 receptor in the pylorus.<\/p>\n
So what does this mean for treatment?<\/b><\/p>\n
Clini\u00adcally, the effect was measurable: In a meta-analysis of three cohorts with 1,119 parti\u00adci\u00adpants, the reduc\u00adtion in HbA1c under GLP-1RA therapy was lower in p.S539W carriers than in non-carriers. This diffe\u00adrence was not observed for metformin, sulfo\u00adnylu\u00adreas, and DPP\u20114 inhibitors.<\/p>\n
This does not yet change any guide\u00adlines. But PAM could help iden\u00adtify GLP-1RA non-respon\u00adders earlier \u2014and make treat\u00adment decis\u00adions less based on the prin\u00adciple of \u201clet\u2019s see if it works.\u201d<\/p>\n