Insulin and the blood-brain barrier

Rare Homozygous Variants in INSR and NFXL1 Are Associated with Severe Treatment-Resistant Psychosis

Psychosis constitutes a cardinal component of schizophrenia and affects nearly fifty percent of those with bipolar disorder. We sought to molecularly characterize psychosis segregating in consanguineous families. Participants from eight multiplex families were evaluated using standardized testing tools. DNA was subjected to exome sequencing followed by Sanger sequencing. Effects of variants were modeled using in-silico tools, while cDNA from a patient's blood sample was analyzed to evaluate the effect of a splice-site variant. Twelve patients in six families were diagnosed with schizophrenia, whereas four patients from two families had psychotic bipolar disorder. Two homozygous rare deleterious variants in INSR (c.2232-7T>G) and NFXL1 (c.1322G>A; p.Cys441Tyr) were identified, which segregated with severe treatment-resistant psychosis/schizophrenia in two families. There were none, or ambiguous findings in the other six families. The predicted deleterious missense variant affected a conserved amino acid, while the intronic variant was predicted to affect splicing. However, cDNA analysis from a patient's blood sample did not reveal an aberrant transcript. Our results indicate that INSR and NFXL1 variants may have a role in psychosis that requires to be investigated further. Lack of molecular diagnosis in some patients suggests the need for genome sequencing to pinpoint the genetic causes.

Antidiabetic GLP-1 Receptor Agonists Have Neuroprotective Properties in Experimental Animal Models of Alzheimer's Disease

In addition to the classically accepted pathophysiological features of Alzheimer's disease (AD), increasing attention is paid to the role of the insulin-resistant state of the central nervous system. Glucagon-like peptide-1 receptor (GLP-1R) agonism demonstrated neuroprotective consequences by mitigating neuroinflammation and oxidative damage. The present review aims to offer a comprehensive overview of the neuroprotective properties of GLP-1R agonists (GLP-1RAs), with a particular focus on experimental animal models of AD. Ameliorated amyloid-β plaque and neurofibrillary tangle formation and deposition following exenatide, liraglutide, and lixisenatide treatment was confirmed in several models. The GLP-1RAs studied alleviated central insulin resistance, as evidenced by the decreased serine phosphorylation of insulin receptor substrate 1 (IRS-1) and restored downstream phosphoinositide 3-kinase/RAC serine/threonine-protein kinase (PI3K/Akt) signaling. Furthermore, the GLP-1RAs influenced multiple mitogen-activated protein kinases (extracellular signal-regulated kinase: ERK; c-Jun N-terminal kinase: JNK, p38) positively and suppressed glycogen synthase kinase 3 (GSK-3β) hyperactivation. A lower proportion of reactive microglia and astrocytes was associated with better neuronal preservation following their administration. Finally, restoration of cognitive functions, particularly spatial memory, was also observed for semaglutide and dulaglutide. GLP-1RAs, therefore, hold promising disease-modifying potential in the management of AD.