Relationship Between Aldosterone and the Metabolic Syndrome in Patients with Obstructive Sleep Apnoea Hypopnoea Syndrome

Relationship between Aldosterone and the Metabolic Syndrome in Patients with Obstructive Sleep Apnoea Hypopnoea Syndrome: Effect of Continuous Positive Airway Pressure Treatment

There have been no sufficient studies to delineate the relationship that exists between obstructive sleep apnoea-hypopnoea syndrome (OSAHS) and metabolic syndrome. Observational studies have unearthed specific relationships between the Renin-Angiotensin-Aldosterone system and hypertension; and between aldosterone and metabolic syndrome.

Findings from the studies show that the levels of aldosterone are quite high in blood in people with OSAHS. The high aldosterone levels are associated with impaired pancreatic β-cell function and insulin resistance. Hence the high levels of aldosterone are seen with the prevalence of metabolic syndrome and can be a very good predictor of the onset of hypertension. Additional clinic trials on antihypertensive agents have shown that direct inhibitors of the Renin-Angiotensin-Aldosterone (RAS) system usually improve insulin sensitivity and to such extent minimize the risk of diabetes.

To find out if hyperaldosteronism is more prevalent in obstructive sleep apnoea-hypopnoea syndrome patients and is associated with metabolic syndrome, a study was set up. Patients with OSAHS, those with and without metabolic syndrome, were tested for plasma aldosterone concentrations (PAC) and plasma aldosterone: renin activity (PRA) ratio. The evaluation was repeated for all the OSAHS patients after a period of 12 months in which effective treatment with continuous positive airway pressure (CPAP) was undertaken. Patients with metabolic syndrome were used as the controls.

The study subjects were 66 male patients with OASHS matched against a set criteria. 33 of the patients had metabolic syndrome while the other 33 did not have metabolic syndrome. They were equally matched for age such that the range was ±5 years and for BMI the range was ±3 Kg.m⁻². None of the participants suffered from any chronic disease such as diabetes, chronic obstructive pulmonary disease (COPD), liver cirrhosis, thyroid dysfunction, rheumatoid arthritis, chronic renal failure. The patients were studied at diagnosis and after effective treatment.

The results of the study indicated that aldosterone levels within blood are associated with the severity of OSAHS. The aldosterone levels are also associated with presence of metabolic syndrome and it aggravates or predisposes metabolic and cardiovascular complication brought about OSAHS. Overall, the relationship between OSAHS and the renin-angiotensin-aldosterone system is complex.

High aldosterone levels in blood can be seen in obese people. Elevated aldosterone levels lead not only to sodium retention and volume expansion, but also to increased inflammation and oxidative stress, which in turn promote insulin resistance, impaired pancreatic β cell function, endothelial dysfunction and hypertension. A recent study demonstrated that in patients with hypertension, plasma aldosterone levels were higher in the group with MS in spite of no differences in plasma renin activity between the groups with or without MS.

Tthe prevalence of metabolic syndrome is higher in OSAHS patients than in the general population even though the biological mechanisms underlying this association between OSAHS and MS are not yet fully understood. Patients with OSAHS and metabolic syndrome had higher levels of glucose than patients without MS.

Lastly, treatment of OSAHS through CPAP therapy reduces aldosterone levels.

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0084362

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