Chronic AT1 blockade improves glucose homeostasis in obese OLETF rats

Area of Science:

• Metabolic research
• Cardiovascular research
• Endocrinology

Background:

• Obesity activates the renin-angiotensin system (RAS), leading to hypertension, impaired insulin secretion, and insulin resistance.
• RAS blockade offers therapeutic benefits, but the impact of treatment duration and disease state on these benefits is unclear.

Purpose of the Study:

• To compare the effects of acute versus chronic angiotensin receptor type 1 (AT1) blockade on pancreatic function and insulin resistance in obese rats.
• To investigate if treatment duration influences the beneficial effects of AT1 blockade on insulin secretion and sensitivity after the onset of metabolic dysfunction.

Main Methods:

• Rats were divided into lean controls, untreated obese rats (OLETF), and obese rats treated with an AT1 receptor blocker (ARB).
• Assessments included adipocyte morphology, glucose tolerance, pancreatic redox balance, and insulin secretion after 2 and 11 weeks of AT1 blockade.
• Measurements of systolic blood pressure, plasma triglycerides, and fasting glucose were taken.

Main Results:

• Both acute and chronic AT1 blockade reduced systolic blood pressure and fasting triglycerides.
• Chronic AT1 blockade significantly decreased fasting glucose (by 22%), glucose intolerance (by 36%), and large adipocyte abundance (by 70%).
• AT1 blockade did not improve pancreatic oxidative stress or reverse impaired insulin secretion.

Conclusions:

• AT1 blockade, initiated after the onset of obesity, hyperglycemia, and hypertension, enhances peripheral insulin sensitivity.
• However, AT1 blockade cannot fully reverse compromised insulin secretion in established metabolic derangement.
• Chronic treatment duration is crucial for improving glucose homeostasis and reducing adipocyte size in this model.