Enhanced mTOR complex 1 signaling attenuates diabetic cardiac injury in OVE26 mice

Area of Science:

• Cardiovascular Research
• Metabolic Diseases
• Cell Signaling

Background:

• The mechanistic target of rapamycin (mTOR) pathway, particularly mTOR complex 1 (mTORC1), is implicated in heart disease.
• Increased mTORC1 activity is observed in diabetic hearts, but its role in diabetic cardiomyopathy is debated.
• Rapamycin, an mTORC1 inhibitor, has yielded conflicting results regarding its effects on diabetic heart conditions.

Purpose of the Study:

• To investigate the functional significance of mTORC1 signaling in the diabetic heart.
• To determine whether enhanced or inhibited mTORC1 activity impacts diabetic cardiac damage.
• To clarify the role of mTORC1 in diabetic cardiomyopathy, contrasting with rapamycin's effects.

Main Methods:

• Crossed OVE26 type 1 diabetic mice with transgenic mice expressing constitutively active (mTORca) or kinase-dead (mTORkd) mTOR in the heart.
• Assessed the specific effects of mTORca and mTORkd on mTORC1 and mTORC2 activities.
• Evaluated cardiac function, oxidative stress, and myocyte apoptosis in diabetic mice with altered mTORC1 signaling.

Main Results:

• Expression of mTORca or mTORkd selectively altered mTORC1 activity without affecting mTORC2.
• Changes in mTORC1 activity correlated with alterations in autophagy, a downstream pathway.
• Diabetic cardiac damage was significantly reduced by mTORca and exacerbated by mTORkd expression.
• Cardiac function improved, oxidative stress decreased, and myocyte apoptosis was reduced in diabetic hearts with enhanced mTORC1 signaling.

Conclusions:

• Enhanced mTORC1 signaling in the diabetic heart is an adaptive mechanism that mitigates cardiac dysfunction and injury.
• Targeting mTORC1 to enhance its activity may offer a therapeutic strategy for diabetic cardiac complications.
• These findings challenge the conventional view of mTORC1 inhibition as beneficial in diabetic heart disease, as suggested by rapamycin studies.