Metformin and high blood pressure
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Metformin and High Blood Pressure: A Comprehensive Review
Introduction to Metformin and Hypertension
Metformin, a widely used antihyperglycemic agent for type 2 diabetes mellitus, has been investigated for its potential effects on blood pressure (BP). This article synthesizes current research on the relationship between metformin and high blood pressure, highlighting key findings from various studies.
Metformin's Impact on Blood Pressure in Hypertensive Rats
Salt-Induced Hypertension
Research on spontaneously hypertensive rats has shown that metformin can attenuate salt-induced hypertension. In a study where rats were fed a high-salt diet, metformin significantly blunted the rise in blood pressure compared to control groups. This effect was attributed to a reduction in sympathetic neural outflow, suggesting that metformin's chronic depressor actions are enhanced in conditions of exacerbated hypertension due to high salt intake.
Metformin's Effects in Hypertensive, Obese Women
Cardiovascular and Metabolic Improvements
In a study involving obese, nondiabetic, hypertensive women, metformin treatment led to significant reductions in blood pressure, left ventricular mass, and various metabolic parameters. The improvements in glucose metabolism and lipid profiles were also noted, indicating a more favorable cardiovascular risk profile with metformin treatment.
Clinical Trials on Metformin and Blood Pressure
Ambulatory Blood Pressure Monitoring
A randomized clinical trial evaluated the effect of metformin on blood pressure using ambulatory blood pressure monitoring (ABPM) in hypertensive patients without diabetes. The study found no significant difference in blood pressure reduction between the metformin and placebo groups, suggesting that metformin may not have a direct BP-lowering effect in non-diabetic hypertensive patients.
Polycystic Ovary Syndrome (PCOS)
In women with PCOS, metformin therapy resulted in reduced systolic blood pressure, along with improvements in insulin resistance and hyperandrogenemia. These findings suggest that metformin can positively impact blood pressure in conditions associated with insulin resistance.
Metformin and High-Fat Diet-Induced Hypertension
Experimental Models
In rats fed a high-fat diet, metformin reduced systolic blood pressure and improved metabolic parameters. The study indicated that metformin's antihypertensive effects might be mediated through the reduction of vasoconstrictor prostanoids, thereby decreasing peripheral resistance.
Systematic Reviews and Meta-Analyses
Blood Pressure and Lipid Profile
A systematic review and meta-analysis of randomized controlled trials in type 2 diabetes patients found that metformin did not significantly affect systolic or diastolic blood pressure. However, it did reduce total and LDL cholesterol levels, suggesting that its cardiovascular benefits might be more related to lipid profile improvements rather than direct BP reduction.
Postprandial Blood Pressure Regulation
Acute Effects in Type 2 Diabetes
Metformin has been shown to attenuate the postprandial fall in blood pressure in patients with type 2 diabetes. This effect is associated with increased GLP-1 secretion and delayed gastric emptying, which may contribute to its favorable cardiovascular profile.
Conclusion
The evidence on metformin's effects on blood pressure is mixed. While some studies suggest beneficial effects in specific conditions like salt-induced hypertension and PCOS, others indicate no significant impact in non-diabetic hypertensive patients. Metformin's cardiovascular benefits may be more pronounced through improvements in metabolic parameters and lipid profiles rather than direct blood pressure reduction. Further research is needed to fully understand the mechanisms and potential clinical applications of metformin in managing hypertension.
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