Blood sugar

Lower blood sugar is generally understood as the amount of glucose fraction ( glucose ) in the blood. Glucose is an important energy source of the body. The brain, red blood cells and the renal medulla are dependent on glucose for energy, all other body cells generate energy primarily in fat metabolism. Glucose is able to cross the blood -brain barrier, and so supplies the brain.

In medicine, the blood glucose level is an important measurement. It is permanently increased, is usually in the diabetes mellitus.

A hypo can reduce the brain performance, seizures, cause increased release of adrenaline and shaky hands and sweats. In marked form the hypoglycaemia leads to shock. It is typically found in the very rare insulinoma, in some cases, but also as an early symptom of type 2 diabetes, often without any other diseases after a meal with rapidly absorbable carbohydrates. In the treatment of diabetes mellitus is a common complication of some medications.

Blood glucose monitoring

The blood sugar is measured from a blood sample is usually from capillary blood. To distinguish the view of measurement accuracy are the measurements by the patients themselves using blood glucose meters and higher quality laboratory measurements.

The unit of measurement unit mmol / l ( millimoles per liter ) is used in most countries, the SI -compliant (International System of Units). In the western part of Germany ( and Berlin ) is as in the U.S., Poland, France, Japan and Austria in the rule nor the older unit mg / dl used (milligrams per deciliter, synonymously also mg %).

For a time, were instruments in circulation that could display the result in either mg / dl or mmol / l. According to the Federal Institute for Drugs and Medical Devices, this led in several cases to confusion of the underlying unit, which had a wrong dosage of insulin result. Therefore, since the fourth quarter of 2006 convertible devices have been withdrawn from the market. A similar problem existed in Switzerland. Since the conversion factor is larger than the usual fluctuations in blood sugar levels, is to identify themselves with the order of the read value, the unit of measurement is displayed. Values ​​less than 25 is likely mmol / l information, probably greater than 25 mg / dl.

Conversion:

Blood sugar levels can start with small blood glucose meters that can be purchased with optional factory- programmed units either in mmol / l or mg / dl can be determined very quickly and largely reliable.

Normal values

When humans are the normal values ​​:

• Sober: 70-99 mg / dl, corresponding to 3.9 to 5.5 mmol / l
• After a carbohydrate-rich meal: up to a maximum of 160 mg / dl, according to 8.9 mmol / l
• Less than 140 mg / dl after 2 hours, corresponding to 7.8 mmol / l

However, the values ​​depending on the literature source and study material ( venous plasma, venous whole blood or capillary whole blood - see tables) different. Values ​​for fasting blood glucose ( FBG ) > 5.5 mmol / l or> 99 mg / dl (according to other sources of > 6.1 mmol / l or 110 mg / dl ) indicate an impaired glucose tolerance close, fasting values ​​> 125 mg / dl to diabetes mellitus. As a complication significantly higher levels of lead in the context of a wound treatment in a prolonged or impaired wound healing. If necessary, then it must be treated to enhance wound healing with insulin at diagnosis of diabetes mellitus.

Abbreviations in the table above

• IFG = impaired fasting glucose (literally, impaired fasting glucose)
• IGT = impaired glucose tolerance (literally, impaired glucose tolerance)

Too high a blood sugar value is called hyperglycemia, hypoglycemia too low. A special form of hemoglobin, HbA1c, is able to reproduce the blood sugar curve over a maximum of three months and is therefore also called the " glycemic memory". Hemoglobin is the red blood pigment in red blood cells that transports oxygen. HbA1c is hemoglobin, which was non-enzymatically glycated due to high blood sugar concentration. The HbA1c gives information about the last three months, as the life of erythrocytes is 120 days.

Measurement methods

The blood glucose monitoring systems for self-monitoring three measurement methods have been basically established.

Optical measurement

In the optical measurement, the blood is drawn in the test strip via a capillary into a visible from outside the test field. Where various chemical substances are incorporated, which react with the blood and have a color change of the test field for the episode. This color change is detected by the instrument and determined by the duration and intensity of the change in blood sugar levels.

Amperometric measurement

In the amperometric measurement, the blood is drawn in the test strip through a capillary in a test field. In test field, the blood is in contact with glucose oxidase and at different electrodes. The meter applies these electrodes to a defined electrical voltage ( 300-600 mV) and measuring over time the current flow, which flows across the electrodes. From the measured current, the device determines the blood sugar levels. The current is proportional to the glucose concentration of the liquid in the containment ( the sensor area of the capillary ).

Non-invasive measurement

In injury-free, so-called non-invasive methods, the blood sugar level to be shown, persecuted or recorded over time, without having to remove the blood. Basically is possible with these and similar methods of measurement a permanent record or representation of the time course (monitoring) of blood glucose levels.

• An optical spectral analysis of very well-vascularized fundus can provide very accurate values ​​. This can include a passive implanted microsensor in mind to increase the quality of the measurements.
• With a permanently implanted micro spectrometer with no moving parts, the spectroscopic measurement of blood glucose in the near infrared range (NIR ) carried (IR spectroscopy). This sensor transmits its measured values ​​with a passive transponder on a display device.
• With a broad-band laser in the mid-infrared (MIR ) can through the skin without injury to the blood sugar level to be measured.

These and other non-invasive methods are still in the research or in clinical approval ( especially in the U.S. ). A new development on the American Northeastern University in Boston, a glucose - sensitive nanosensor, the nanoparticles are injected on the type of Tattoos and fluoresce at elevated blood sugar levels.

A market introduction of noninvasive blood glucose measurement by spectroscopic measurement techniques in the field of near-infrared ( NIR) with extra corporal measuring devices failed so far because the devices ie glucose per volume of the irradiated body tissue, not blood glucose per volume of blood to determine the tissue sugar, because of the measurement beam must penetrate the body tissue for the measurement.

Determination of glucose in urine

Further measurement of the Harnglucosewertes is possible. Glucose can, however, only be detected in the urine when the glucose concentration is greatly increased and has exceeded a certain value. This value is dependent on the so-called renal threshold of the respective subjects. These renal threshold is very unreliable and easily be interfered with. As in pregnancy, the renal threshold drop below 120 mg / dl in healthy individuals, it can also more than 200 mg / dl. Even mild kidney disease may alter the renal threshold. Due to the relatively high reliability and good availability of blood glucose monitors at the same high prices for the gauges to determine the urinary sugar can be considered obsolete.

Regulation

The blood sugar level is regulated by the interplay of two peptide hormones of the pancreas ( pancreatic ). This gland contains in its α - and β - cell glucose - sensor systems that respond as follows:

• In waste sugar levels in the blood ( " hunger signal" ) is secreted glucagon. This hormone is activated in the liver glycogen phosphorylase ( PYG), which initiates the breakdown of glycogen to glucose ( catabolic branch) (upper panel )

• Increase in the blood sugar level insulin is secreted, which particularly in the liver, a series of glucose - consuming reactions initiated (anabolic branch). Of central importance here is the indirect activation of glycogen synthase ( GYS ), the glucose - excess to build up the energy store glycogen ( " animal starch " ) uses (lower panel )

In addition, the same reaction is triggered in muscle cells as glucagon acts on the liver cells by epinephrine.

Glykogenab and build-up are on the phosphorylation of key enzymes of glycogen phosphorylase ( PYG) and glycogen synthase ( GYS ) strictly regulated in opposite directions, so never run simultaneously. In energy shortages both enzymes are phosphorylated by kinases; This process stimulates the phosphorylase, but inhibits synthase. When glucose excess the situation by the action of phosphatases is turned into the opposite: loss of phosphate residues inactivated PYG activated but GYS.

Both glucagon and insulin signaling are amplified by signaling cascades. At the center of both signaling pathways are protein kinases: Each kinase phosphorylates several molecules of a downstream kinase.

• In the case of the glucagon and epinephrine a G protein -dependent receptor (GPCR, seven-transmembrane helix - type) is controlled. Via the Gs - protein activated adenylyl cyclase, an enzyme which produces the second messenger cAMP. Thereby, the protein kinase A (PKA) cascade is initiated at the end of which is glycogen phosphorylase ( PYG). After phosphorylation to be activated (PYG a). This releases glucose -1-phosphate from glycogen, which is isomerized to glucose-6- phosophat and can enter the glycolysis. At the same PKA phosphorylates the glycogen synthase ( GYS a), the ( GYS b ) is in its inactive phosphorylated form.

• In the case of the insulin receptor tyrosine kinase is activated ( RTK). On the way, a complex signal transduction is here including the protein kinase B (PKB ) is activated ( see picture below, A). PKB phosphorylates glycogen synthase kinase - 3, GSK3, which is thereby inactivated. GSK3 is a kinase that phosphorylates and thereby inactivates glycogen synthase ( GYS b). GSK3 is competing with a phosphatase, protein phosphatase 1 (PP1 ). Because GSK3 can no longer act, therefore increasing glycogen synthase lies in its dephosphorylated form ( GYS a, see picture below, B). In addition, the PKB activates a phosphodiesterase PDE hydrolyzes cAMP to AMP. As a result, in addition, the signal goes out for the PCA.