Interaction between specific fatty acids, GLP-1 and insulin secretion in humans

Area of Science:

• Endocrinology
• Metabolism
• Human Physiology

Background:

• Fatty acids are known to influence insulin secretion in vivo.
• Limited understanding exists regarding the specific effects of individual fatty acids on this process.

Purpose of the Study:

• To investigate the differential effects of acute increases in plasma monounsaturated (MUFA), polyunsaturated (PUFA), and saturated (SFA) fatty acids on glucose-stimulated insulin secretion in healthy humans.

Main Methods:

• A novel protocol involved increasing plasma non-esterified fatty acids (NEFA) using oral fat loading and heparin infusion.
• A hyperglycaemic clamp was employed to assess insulin secretion following elevated NEFA levels.
• Specific tests were conducted for MUFA, PUFA, and SFA.

Main Results:

• Plasma NEFA concentrations significantly increased during all fat tests compared to control.
• Exaggerated insulin, C-peptide, and proinsulin responses were observed post-NEFA increase.
• Monounsaturated fatty acids demonstrated the most pronounced effect, followed by polyunsaturated and saturated fatty acids.
• Plasma GLP-1 concentrations increased, with MUFA eliciting a greater response than PUFA and SFA.

Conclusions:

• Acute elevation of plasma NEFA through oral fat feeding augments glucose-stimulated insulin secretion.
• Monounsaturated fatty acids exhibit the strongest stimulatory effect on insulin secretion, whereas saturated fatty acids show the weakest.
• The enhanced insulin response may be attributed to both elevated NEFA and increased GLP-1 levels, particularly with MUFA.