SORCS2 activity in pancreatic α-cells safeguards insulin granule formation and release from glucose-stressed β-cells

SorCS2 Is Important for Astrocytic Function in Neurovascular Signaling

INTRODUCTION

The receptor SorCS2 is involved in the trafficking of membrane receptors and transporters. It has been implicated in brain disorders and has previously been reported to be indispensable for ionotropic glutamatergic neurotransmission in the hippocampus.

AIM

We aimed to study the role of SorCS2 in the control of astrocyte-neuron communication, critical for neurovascular coupling.

METHODS

Brain slices from P8 and 2-month-old wild-type and SorCS2 knockout (Sorcs2-/-) mice were immunostained for SorCS2, GFAP, AQP4, IB4, and CD31. Neurovascular coupling was assessed in vivo using laser speckle contrast imaging and ex vivo in live brain slices loaded with calcium-sensitive dye. Bulk and cell surface fraction proteomics was analyzed on freshly isolated and cultured astrocytes, respectively, and validated with Western blot and qPCR.

RESULTS

SorCS2 was strongly expressed in astrocytes, primarily in their endfeet, of P8 mice; however, it was sparsely represented in 2-month-old mice. Sorcs2-/- mice demonstrated reduced neurovascular coupling associated with a reduced astrocytic calcium response to neuronal excitation. No differences in vascularization or endothelium-dependent relaxation ex vivo between the 2-month-old groups were observed. Proteomics suggested changes in glutamatergic signaling and suppressed calcium signaling in Sorcs2-/- brains from both P8 and 2-month-old mice. The increased abundance of glutamate metabotropic receptor 3 in Sorcs2-/- astrocytes was validated by PCR and Western blot. In cultured Sorcs2-/- astrocytes, AQP4 abundance was increased in the bulk lysate but reduced in the cell surface fraction, suggesting impaired trafficking.

CONCLUSION

The results suggest that SorCS2 expression is important for the development of neurovascular coupling, at least in part by modulating glutamatergic and calcium signaling in astrocytes.

Genetic Variants Linked to Myocardial Infarction in Individuals with Non-Alcoholic Fatty Liver Disease and Their Potential Interaction with Dietary Patterns

In recent studies, non-alcoholic fatty liver disease (NAFLD) has been associated with a high risk of ischemic heart disease. This study aimed to investigate a genetic variant within a specific gene associated with myocardial infarction (MI) among patients with NAFLD. We included 57,205 participants from a Korean genome and epidemiology study. The baseline population consisted of 45,400 individuals, with 11,805 identified as patients with NAFLD. Genome-wide association studies were conducted for three groups: the entire sample, the healthy population, and patients with NAFLD. We defined the p-value < 1 × 10-5 as the nominal significance and the p-value < 5 × 10-2 as statistically significant for the gene-by-nutrient interaction. Among the significant single-nucleotide polymorphisms (SNPs), the lead SNP of each locus was further analyzed. In this cross-sectional study, a total of 1529 participants (2.8%) had experienced MI. Multivariable logistic regression was performed to evaluate the association of 102 SNPs across nine loci. Nine SNPs (rs11891202, rs2278549, rs13146480, rs17293047, rs184257317, rs183081683, rs1887427, rs146939423, and rs76662689) demonstrated an association with MI in the group with NAFLD Notably, the MI-associated SNP, rs134146480, located within the SORCS2 gene, known for its role in secreting insulin in islet cells, showed the most significant association with MI (p-value = 2.55 × 10-7). Our study identifies candidate genetic polymorphisms associated with NAFLD-related MI. These findings may serve as valuable indicators for estimating MI risk and for conducting future investigations into the underlying mechanisms of NAFLD-related MI.