In this video collection, authors of findings published in The Journal of Clinical Investigation present personally guided tours of their results. The journal accepts video submissions from authors of recently accepted manuscripts. Instructions can be found on the Author's Take Guidelines page.
There is a strong association between obesity and type 2 diabetes (T2D); however, the majority of obese individuals do not develop T2D, supporting that genetic predisposition is an important component of the disease. Alan Attie and colleagues previously revealed that polymorphisms in the Sorcs1 gene are associated with diabetes in obese mice. In this episode, Alan Attie, Angie Oler, and Melkam Kebede discuss their current study, which demonstrates that SORCS1 is required to replenish insulin secretory granules. Although obese Sorcs1-defient mice developed severe T2D, insulin secretion in response to a single glucose challenge did not appear dysfunctional in these animals. However, repeated challenge of islets isolated from Sorcs1-deficient mice resulted in loss of secretory granule production and insulin content. These results suggest that some insulin secretion defects in patients may not be revealed by a single secretagogue challenge.
Age-related declines in immune function result in enhanced susceptibility to infection and decreased vaccine efficacy. While aged immune cells exhibit signs of cellular senescence, such as a reduced proliferative capacity, many maintain effector function. In this episode, Sian Henson discusses the characterization of a subset of human effector memory CD8+ T cells that reexpress the naïve T cell marker CD45RA (EMRA cells). Despite their senescent-like state, EMRA cells exhibited potent cytotoxic activity, the energy for which was generated by anaerobic glycolysis. Inhibition of p38 MAPK signaling in EMSA cells reversed senescent phenotypes and increased autophagy. These results indicate that some aspects of CD8+ T cell senescence may be reversible.
β cell dysfunction is a hallmark of type 2 diabetes (T2D) and is associated with extracellular accumulation of amyloid plaques comprised of islet amyloid polypeptide (IAPP). Human IAPP is potentially toxic and has been shown to accumulate within β cells of T2D patients and in transgenic rodent models. In this episode, Safia Costes and colleagues examine the role of autophagy in the degradation of human IAPP in murine models. Human IAPP aggregated within p62-positive inclusions in transgenic animals, with no apparent loss of β cell function or mass; however, human IAPP-expressing mice with a β cell-specific autophagy defect developed overt diabetes due β cell death. These results indicate that autophagy is protective against IAPP-induced toxicity in β cells and suggest the autophagy pathway as a potential theraputic target for treatment and/or prevention of T2D.
In virto fertilization (IVF) has helped millions of couples have children. While considered relatively safe, there are risks associated with this procedure. Among the more serious complications is the development of ovarian hyperstimulation syndrome (OHSS), which in extreme cases can be fatal. OHSS results from excessive stimulation of the luteinizing hormone (LH) receptor by human chorionic gonadotropin (hCG), which is commonly used as part of the IVF cycle to promote egg maturation. In this episode, Waljit Dhillo discusses the results from a small clinical trial that evaluated use of the fertility hormone kisspeptin-54 for egg maturation in IVF. Dhillo and colleagues report that kisspeptin-54 treatment resulted in mature eggs that were successfully fertilized and transferred, with pregnancy in 23% of patients.
Fibrosis is a hallmark of chronic kidney disease that is characterized by accumulation of extracellular matrix and an influx of immune cells. Autophosphorylation of serine residues within the type II TGF-β receptor (TβRII) following activation by TGF-β induces a SMAD-dependent profibrotic signaling cascade; however, there are multiple tyrosine residues within the cytoplasmic tail of TβRII that have potential to regulate this pathway. In this episode, Ambra Pozzi reveals that phosphorylation of tyrosine residues in the cytoplasmic tail of TβRII does influence the fibrotic signaling cascade. Specifically, Pozzi and colleagues determined that integrin α1β1 recruits the phosphatase TCPTP to TβRII, subsequently dephosphorylating tyrosine residues within the TβRII cytoplasmic tail. Furthermore, mice lacking α1β1 integrin exhibited enhanced phosphorylation of TβRII due to decreased recruitment of TCPTP, resulting in severe fibrosis following kidney injury.