Glucagon may be extracted across the liver by a glucagon receptor-dependent mechanism, and this is impaired in an animal model of fatty liver disease

Hyperglucagonemia is a hallmark of metabolic diseases including type 2 diabetes and metabolic dysfunction-associated steatotic liver disease (MASLD), yet the underlying mechanisms are unclear. This study aimed to characterize the liver's role in glucagon clearance and to elucidate whether enzymatic degradation or receptor-mediated uptake is the dominant clearance mechanism-particularly in the context of obesity-associated hepatic steatosis. Using an in situ perfused single-pass mouse liver model, hepatic glucagon clearance/disappearance was quantified directly in lean and diet-induced obese (DIO) male C57BL/6JRj mice. Glucagon disappearance across the liver was measured via immunoassays and mass spectrometry. To dissect the mechanism of clearance, glucagon was coinfused with either enzyme inhibitors [for dipeptidyl peptidase 4 (DPP-4) and neprilysin (NEP)] or a glucagon receptor antagonist. In lean mice, the liver extracted 20% of inflowing portal venous glucagon (at levels corresponding to postprandial conditions), an effect abolished by glucagon receptor antagonism but unaffected by enzyme inhibition. Mass spectrometry confirmed that nearly all glucagon remained intact, supporting receptor-mediated internalization as the primary clearance mechanism. In DIO mice with hepatic steatosis determined as elevated hepatic triglyceride content, glucagon clearance was markedly reduced. The glucagon receptor was downregulated in livers of DIO mice. These findings identify the liver as an active site of glucagon clearance, potentially through receptor-mediated mechanisms. Obesity-related hepatic steatosis disrupts this process and may contribute to hyperglucagonemia in metabolic disease. Targeting hepatic glucagon clearance may offer a novel approach to normalize glucagon levels and improve metabolic control.<b>NEW & NOTEWORTHY</b> We identify the liver as an active glucagon-clearing organ: ∼20% of portal glucagon is extracted under physiological conditions via glucagon receptor-dependent uptake, not enzymatic cleavage. DPP-4 and neprilysin inhibition does not alter hepatic glucagon disappearance, and mass spectrometry confirms glucagon remains largely intact. Strikingly, diet-induced hepatic steatosis nearly abolishes glucagon extraction, coinciding with reduced hepatic GCGR expression, suggesting impaired receptor-mediated clearance may contribute to hyperglucagonemia in MASLD.