β-Cell Insulin Resistance Plays a Causal Role in Fat-Induced β-Cell Dysfunction In Vitro and In Vivo

Area of Science:

• Endocrinology
• Metabolic Research
• Cellular Signaling

Background:

• Chronically elevated free fatty acids (FFA) impair insulin signaling in classical target tissues.
• Insulin signaling pathways are also present in pancreatic beta cells, influencing their function.
• Fat-induced beta-cell dysfunction may involve the inhibition of the insulin/insulin-like growth factor 1 pathway.

Purpose of the Study:

• To investigate the role of beta-cell insulin resistance in free fatty acid (FFA)-induced beta-cell dysfunction.
• To determine if enhancing insulin signaling can protect beta cells from FFA-induced impairment.

Main Methods:

• Rats were co-infused with oleate/olive oil and bisperoxovanadate (BPV), a tyrosine phosphatase inhibitor and insulin mimetic.
• Beta-cell function was assessed in vivo using hyperglycemic clamps and ex vivo via glucose-stimulated insulin secretion (GSIS) assays.
• In vitro studies involved incubating islets with fatty acids and BPV to assess GSIS and Akt phosphorylation.
• Mice with beta-cell specific deletion of PTEN (phosphatase and tensin homolog) were infused with oleate and evaluated for beta-cell function.

Main Results:

• BPV administration protected rat beta cells from fat-induced functional impairment across in vivo, ex vivo, and in vitro settings.
• Beta-cell specific deletion of PTEN in mice conferred protection against oleate-induced beta-cell dysfunction.
• These findings indicate that impaired insulin signaling (insulin resistance) within beta cells is a key factor in FFA-induced dysfunction.

Conclusions:

• Beta-cell insulin resistance plays a causal role in free fatty acid-induced beta-cell dysfunction.
• Targeting insulin signaling pathways within beta cells may offer a therapeutic strategy for managing fat-induced beta-cell impairment.