MiR-335 regulates exocytotic proteins and affects glucose-stimulated insulin secretion through decreased Ca2+-dependent exocytosis in beta cells

• Background and aims: Ca2+-induced exocytosis is essential for insulin to be secreted from beta-cells, and in islets from type-2 diabetic (T2D) donors the expression of several genes coding for exocytotic proteins is reduced. Largely this phenomenon cannot be explained by polymorphism; rather it is likely due to epigenetic factors like microRNAs (miRNAs). Indeed, previous studies have identified a number of miRNAs with differential expression in the islets from T2D donors and the Goto- Kakizaki (GK) rat. One of the upregulatedmiRNAs in the GK rat is miR- 335, predicted to target several exocytotic genes amongst those Stxbp1 is a validated target. Here we aim to investigate whether miR-335 regulates the expression of exocytotic genes and affects insulin secretion and exocytosis in beta-cells. Materials and methods: Insulin secretion was measured by radio immuno assay. Exocytosis and docking of insulin granules was studied by capacitance measurements using the patch-clamp technique and by TIRF microscopy. Rat miR-335 was overexpressed using chemicallymodified mature microRNA mimic in INS-1 832/13 beta-cells by transfection. Gene knockdown was performed with RNAi. Protein and mRNA levels were analysed with Western Blot and RT-qPCR, respectively. Results: Overexpression of miR-335 (OE335) in INS-1 832/13 cells reduced insulin secretion at 16.7 mM glucose compared to control cells (SCR) (n=3; p

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Endokrinologi och diabetes (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Endocrinology and Diabetes (hsv//eng)

Nyckelord

glucose

protein

insulin

microRNA

synaptotagmin

nitrogen 15

messenger RNA

insulin release

exocytosis

European

diabetes mellitus

gene

microscopy

donor

membrane

Goto Kakizaki rat

rat

genetic transfection

patch clamp technique

immunoassay

gene silencing

pancreas islet beta cell

density

electric potential

Western blotting

adaptation

cell function

telecommunication

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kon (ämneskategori)

ref (ämneskategori)