Related Experiment Video

Updated: May 9, 2026

Human Pseudoislet System for Synchronous Assessment of Fluorescent Biosensor Dynamics and Hormone Secretory Profiles
08:04

Human Pseudoislet System for Synchronous Assessment of Fluorescent Biosensor Dynamics and Hormone Secretory Profiles

Published on: November 3, 2023

A role for SPARC in the moderation of human insulin secretion

Lorna W Harries1, Laura J McCulloch, Janet E Holley

  • 1Institute of Biomedical and Clinical Sciences, Exeter Medical School, University of Exeter, Exeter, United Kingdom. L.W.Harries@exeter.ac.uk

Plos One
|July 11, 2013
PubMed
Abstract

Insights

Secreted protein acidic and rich in cysteine (SPARC) levels are lower in diabetic islets and SPARC enhances glucose-stimulated insulin secretion, suggesting a role in diabetes regulation.

Area of Science:

  • Endocrinology
  • Metabolic Research
  • Molecular Biology

Background:

  • The multifunctional protein SPARC (Secreted protein acidic and rich in cysteine)/osteonectin is implicated in insulin resistance.
  • The specific impact of SPARC on pancreatic beta-cell function remains largely uncharacterized.

Purpose of the Study:

  • To investigate the role of SPARC in pancreatic beta-cell function.
  • To determine the effect of SPARC on diabetes-related features.

Main Methods:

  • SPARC expression was quantified using qRT-PCR in human islets, adipose tissue, liver, and muscle.
  • The correlation between SPARC levels and glucose-stimulated insulin secretion (GSIS) was assessed in human islets.
  • The impact of SPARC overexpression on GSIS was evaluated in beta-cell lines.

Main Results:

  • SPARC was expressed in human islets, adipose tissue, liver, and skeletal muscle.
  • Reduced SPARC expression was observed in islets from individuals with diabetes compared to controls.
  • SPARC levels positively correlated with GSIS in control islets.
  • Overexpression of SPARC significantly increased insulin secretion under high glucose conditions in beta-cells.

Conclusions:

  • SPARC expression is diminished in pancreatic islets of individuals with diabetes.
  • SPARC plays a role in regulating insulin secretion.
  • The observed effect of SPARC on insulin secretion appears independent of its influence on obesity-induced insulin resistance.

More Related Videos

Measuring Relative Insulin Secretion using a Co-Secreted Luciferase Surrogate05:58

Measuring Relative Insulin Secretion using a Co-Secreted Luciferase Surrogate

Published on: June 25, 2019

Related Concept Videos

Glucose Homeostasis: Pancreatic Islets and Insulin Secretion01:27

Glucose Homeostasis: Pancreatic Islets and Insulin Secretion

The pancreatic islets comprising only 1%-2% of the volume are highly vascularized and innervated mini-organs. They contain five endocrine cell types, including β cells that secrete insulin, which is synthesized as a single polypeptide chain, preproinsulin, processed to proinsulin, and finally to insulin and C-peptide. This process is complex and regulated, involving the Golgi complex, the endoplasmic reticulum, and the secretory granules of the β cell.
Insulin and C-peptide are co-secreted in...
Insulin: The Receptor and Signaling Pathways01:28

Insulin: The Receptor and Signaling Pathways

Insulin action is mediated through a receptor tyrosine kinase, akin to the IGF-1 receptor. The number of receptors per cell varies significantly, from 40 on erythrocytes to 300,000 on adipocytes and hepatocytes. The insulin receptor consists of linked α/β subunit dimers, forming a heterotetramer glycoprotein with two extracellular α subunits and two β subunits spanning the membrane. The α subunits inhibit the inherent tyrosine kinase activity of the β subunits, but this inhibition is released...
Hormones Regulating Blood Glucose01:16

Hormones Regulating Blood Glucose

Insulin is released by beta cells of the pancreas when blood glucose levels are high. It facilitates glucose absorption and utilization in insulin-dependent cells with insulin receptors on their plasma membranes. Insulin promotes glucose uptake by increasing the number of glucose transport proteins in the cell membrane, allowing glucose to enter the cell. As a result, glucose utilization and ATP production are enhanced.
In addition to accelerating glucose uptake and utilization, insulin has...
Insulin Secretory Vesicles01:05

Insulin Secretory Vesicles

Insulin secretory vesicles release insulin to stimulate blood glucose uptake and regulate carbohydrate metabolism. When the blood glucose levels increase, glucose enters the pancreatic β-islet cells through glucose transporters. Once inside, glucose is metabolized through glycolysis, the citric acid cycle, and the electron transport chain, producing ATP. This increase in ATP concentration closes ATP-sensitive potassium channels, leading to depolarization of the membrane and the opening of...
Cells and Secretions of the Pancreas01:16

Cells and Secretions of the Pancreas

The pancreas, a vital organ within the abdominal cavity, plays dual roles in the digestive and endocrine systems, collaborating with exocrine and endocrine cells to maintain optimal digestion and blood sugar levels.
Exocrine function is carried out by acinar cells, organized into clusters known as acini. These cells contribute to digestion by releasing substantial quantities of enzyme-rich, alkaline digestive juices.
Concurrently, the dispersed clusters of endocrine cells throughout the...
Insulin: Biosynthesis, Chemistry, and Preparation01:25

Insulin: Biosynthesis, Chemistry, and Preparation

The endoplasmic reticulum (ER) of pancreatic β-cells synthesizes preproinsulin, which consists of a signal peptide, A and B chains, and a C-peptide. Preproinsulin is then cleaved and folded into proinsulin, which translocates to the Golgi apparatus for sorting and packaging into secretory granules. In these granules, enzymatic clipping generates insulin and C-peptide.
Damage or functional impairment of β-cells inhibits insulin production, leading to diabetes. Diabetes treatment primarily uses...