If logistics fails, the column stops
Menopause changes the cholesterol metabolism in women, but the exact net impact of this change on health is not yet known, writes Associate Professor Eija Laakkonen from the Faculty of Sport and Health Sciences, Ä¢¹½Ö±²¥.
The cardiovascular system is to sustain the tissues in the body. It transports many types of molecules, carrier complexes and blood cells from the heart through arteria to capillaries and tissues. Blood eventually returns back to the heart through veins. The heart bumps blood rhythmically. This produces a progressive pulse wave, which makes arteria dilate and contract in an alternating rhythm. This pushes blood forward without any reflux.
This is about a sophisticated interplay within the cardiovascular system; the arterial walls need to be adequately but not too flexible, so that the pulse wave can advance without hurting the arterial walls.
Towards old age, the arterial walls become increasingly stiff, which increases the risk for cardiovascular diseases and fatal complications.
In women’s life, menopause turns thoughts to aging. The ovaries’ stop working; the menstrual cycle stops, and hormonal activity changes. Estrogen levels in blood decrease permanently.
Estrogen has many functions. We know that it also contributes to the regulation of the flexibility of the vascular walls. This is considered to be one of the mechanisms owing to which young women have a lower risk of cardiovascular diseases than men of the same age have.
On the other hand, menopause brings along also other hormonal changes. For example, the blood level of follicle stimulating hormone stays permanently high, instead of the previous cyclic variation. In our study, we observed that both of these hormones were connected with arterial stiffness, although age was a still stronger determinant for such stiffness.
Menopause affects LDL and HDL particles as well
In addition to the greater stiffness of arterial walls, blood circulation is also impeded by arterial stenosis. It refers to a situation where LDL cholesterol carried by low-density particles starts to build up underneath the thin film that covers the inner surface of arteria.
This calls on the sanitation troops, i.e. macrophages, which seek to solve the problem by eating up the extra cholesterol. Cholesterol is delivered to high-density lipoprotein particles (HDL ), which carry cholesterol to the liver for disintegration. If this circulation chain is deficient, the cholesterol build-up keeps growing and starts to block the artery. The overall process is slow. It may begin at a young age already and lead to symptoms and illness not until years later.
Menopause affects LDL and HDL particles as well. For health, it would be best to keep the blood levels of LDL cholesterol low and HDL cholesterol high so that the overall cholesterol level would be under 5 mmol/l.
During menopause women’s LDL cholesterol levels and, according to most studies, also HDL cholesterol levels in blood increase.
The change mechanism and net impact on health are not yet known.
HDL particles have also other functions than just to carry cholesterol. They also carry other fats, various proteins and RNA- molecules. The circulating blood contains a variety of differently sized HDL particles with varying compositions.
It is likely that the supply of estrogen affects the composition of HDL particles and thereby their functioning. Thus, a high level of HDL cholesterol indicates that the particles are loaded but not what other components the load includes and whether the transportation advances smoothly or whether the column gets stuck.
Associate Professor Eija Laakkonen works in the fields of gerontology and public health in the Faculty of Sport and Health Sciences, Ä¢¹½Ö±²¥.
