Use of non-invasive diagnostic tools for metabolic dysfunction-associated steatohepatitis: A qualitative exploration of challenges and barriers.

BACKGROUND AND AIMS: Non-invasive tests (NITs) are underutilized for diagnosis and risk stratification in metabolic dysfunction-associated steatotic liver disease (MASLD), despite good accuracy. This study aimed to identify challenges and barriers to the use of NITs in clinical practice. METHODS: We conducted a qualitative exploratory study in Germany, Italy, United Kingdom and United States. Phase 1 participants (primary care physicians, hepatologists, diabetologists, researchers, healthcare administrators, payers and patient advocates; n = 29) were interviewed. Phase 2 participants (experts in MASLD; n = 8) took part in a group discussion to validate and expand on Phase 1 findings. Finally, we triangulated perspectives in a hybrid deductive/inductive thematic analysis. RESULTS: Four themes hindering the use of NITs emerged: (1) limited knowledge and awareness; (2) unclear referral pathways for patients affected by liver conditions; (3) uncertainty over the value of NITs in monitoring and managing liver diseases; and (4) challenges justifying system-level reimbursement. Through these themes, participants perceived a stigma associated with liver diseases, and primary care physicians generally lacked awareness, adequate knowledge and skills to use recommended NITs. We identified uncertainties over the results of NITs, specifically to guide lifestyle intervention or to identify patients that should be referred to a specialist. Participants indicated an ongoing need for research and development to improve the prognostic value of NITs and communicating their cost-effectiveness to payers. CONCLUSIONS: This qualitative study suggests that use of NITs for MASLD is limited due to several individual and system-level barriers. Multi-level interventions are likely required to address these barriers.

Glucagon: the renewal of an old hormone in the pathophysiology of diabetes.

Type 2 diabetes (T2D) is one of the most common diseases, affecting 5-10% of the population in most countries; the progression of its prevalence has been constant over the past 50 years in all countries worldwide, creating a major public health problem in terms of disease management and financial burden. Although the pathophysiology of T2D has been attributed for decades to insulin resistance and decreased insulin secretion, particularly in response to glucose, the contributing role of glucagon in hyperglycemia has been highlighted since the early 1970s by demonstrating its glycogenolytic, gluconeogenic and ketogenic properties. More recently, the importance of glucagon in diabetes has been highlighted in a model of streptozotocin-induced diabetic mice becoming euglycemic in the absence of glucagon receptors and without insulin treatment. Understanding the dysregulation of α-cells in diabetes will be critical to better define the pathophysiology of diabetes and develop new antidiabetic treatment.

Pax6 is crucial for ß-cell function, insulin biosynthesis, and glucose-induced insulin secretion.

The Pax6 transcription factor is crucial for endocrine cell differentiation and function. Indeed, mutations of Pax6 are associated with a diabetic phenotype and a drastic decrease of insulin-positive cell number. Our aim was to better define the ß-cell Pax6 transcriptional network and thus provide further information concerning the role of Pax6 in ß-cell function. We developed a Pax6-deficient model in rat primary ß-cells with specific small interfering RNA leading to a 75% knockdown of Pax6 expression. Through candidate gene approach, we confirmed that Pax6 controls the mRNA levels of the insulin 1 and 2, Pdx1, MafA, GLUT2, and PC1/3 genes in ß-cells. Importantly, we identified new Pax6 target genes coding for GK, Nkx6.1, cMaf, PC2, GLP-1R and GIPR which are all involved in ß-cell function. Furthermore, we demonstrated that Pax6 directly binds and activates specific elements on the promoter region of these genes. We also demonstrated that Pax6 knockdown led to decreases in insulin cell content, in insulin processing, and a specific defect of glucose-induced insulin secretion as well as a significant reduction of GLP-1 action in primary ß-cells. Our results strongly suggest that Pax6 is crucial for ß-cells through transcriptional control of key genes coding for proteins that are involved in insulin biosynthesis and secretion as well as glucose and incretin actions on ß-cells. We provide further evidence that Pax6 represents a key element of mature ß-cell function.

Pax6 is a key component of regulated glucagon secretion.

The Pax6 transcription factor is crucial for pancreatic α-cells. Indeed, Pax6-deficient mouse models are characterized by markedly altered α-cell differentiation. Our objective was to investigate the role of Pax6 in glucagon secretion process. We used a Pax6-deficient model in rat primary enriched-α cells with specific small interfering RNA leading to a 70% knockdown of Pax6 expression. We first showed that Pax6 knockdown decreases glucagon biosynthesis as well as glucagon release. Through physiological assays, we demonstrated that the decrease of Pax6 affects specifically acute glucagon secretion in primary α-cell in response to glucose, palmitate, and glucose-dependent insulinotropic peptide (GIP) but not the response to arginine and epinephrine. We identified in Pax6 knockdown model that genes involved in glucagon secretion such as the glucokinase (GCK), G protein-coupled receptor (GPR40), and GIP receptor (GIPR) as well as the corresponding proteins were significantly decreased whereas the insulin receptor (IR) Kir6.2/Sur1, and glucose transporter 1 genes were not affected. We demonstrated that Pax6 directly binds and activates specific elements on the promoter region of the GPR40, GCK, and GIPR genes. Finally, through site-directed mutagenesis experiments, we showed that disruption of Pax6 binding on the GCK, GPR40, and GIPR gene promoters led to specific decreases of their activities in the αTC1.9 glucagon-producing cell line. Hence our results indicate that Pax6 acts on the regulation of glucagon secretion at least through the transcriptional control of GCK, GPR40, and GIPR. We propose that Pax6 is not only critical for glucagon biosynthesis but also for glucagon secretion particularly in response to nutrients.