Albumin in the urine and diabetic nephropathy

A laboratory criterion characterizing the development of a pronounced stage of diabetic nephropathy is proteinuria (usually with unchanged urine sediment), a decrease in GFR, and an increase in azotemia (concentration of urea and creatinine in the blood serum). In 30% of patients develops a nephrotic syndrome (massive proteinuria - more than 3.5 g / day, hypoalbuminemia, hypercholesterolemia, edema). Since the onset of permanent proteinuria, the rate of decline in GFR is on average 2 ml / min., Which leads to the development of terminal chronic renal failure even 5-7 years after the detection of proteinuria.

Stages of development of diabetic nephropathy

Stage	Clinical and laboratory characteristics	Terms of development
Hyperfunction of the kidneys	Increased GFR more than 140 ml / min Increase in renal blood flow Hypertrophy of the kidneys Normoalbuminuria (less than 30 mg / day)	In the beginning of the disease
Initial structural changes in renal tissue	Thickening of the basal membranes of the glomerular capillaries. Expansion of the mesangium. High GFR is preserved. Normoalbuminuria (less than 30 mg / day)	2-5 years
Beginning Nephropathy	Microalbuminuria (30-300 mg / day) GFR high or normal Low blood pressure increase	5-15 years
Severe nephropathy	Proteinuria (more than 500 mg / day) GFR normal or moderately reduced Arterial hypertension	10-25 years old
Uremia	Reduction of GFR less than 10 ml / min	More than 20 years from the onset of diabetes or 5-7 years from the onset of proteinuria
	Symptoms of intoxication

At the stage of chronic renal insufficiency, laboratory tests allow determining the tactics of managing patients with diabetes mellitus.

• With the development of chronic renal failure in patients with type 1 diabetes mellitus, the daily need for insulin sharply decreases, in connection with this the frequency of hypoglycemic conditions increases, which requires a decrease in the dose of insulin.
• Patients with type 2 diabetes mellitus taking oral hypoglycemic drugs are advised to switch to insulin therapy when developing chronic renal insufficiency, since most of these drugs are metabolized and excreted by the kidneys.
• When the concentration of creatinine in the blood serum is more than 500 μmol / l (5.5 mg%), it is necessary to consider the preparation of the patient for hemodialysis.
• Serum creatinine concentration of 600-700 μmol / l (8-9 mg%) and glomerular filtration rate (GFR) of less than 10 ml / min are considered indications for kidney transplantation.
• An increase in the serum creatinine concentration to 1000-1200 μmol / l (12-16 mg%) and a decrease in GFR of less than 10 ml / min is considered an indication for programmed hemodialysis.

Renal failure associated with diabetic nephropathy is the immediate cause of death in approximately half the cases of type 2 diabetes. It is very important for the clinician to conduct laboratory tests to monitor the dynamics of diabetic nephropathy. According to the recommendation of WHO experts, in the absence of proteinuria, a study on microalbuminuria should be conducted:

• in patients with type 1 diabetes mellitus at least once a year after 5 years from the onset of the disease (if diabetes occurs after puberty) and at least once a year from the time of diagnosis of diabetes at the age of 12 years;
• in patients with type 2 diabetes mellitus, at least once a year from the time of diagnosis.

In normal urinary albumin excretion should strive to maintain the fraction of glycosylated hemoglobin (HbA _{1 c} ) at a level of not more than 6%.

In the presence of proteinuria in patients with diabetes mellitus, the rate of increase of proteinuria (in daily urine) and the rate of reduction of GFR are examined at least once every 4-6 months.

At present, the test for microalbuminuria should be considered as an indicator of the evaluation of the function of plasma membranes of highly differentiated cells. Normally, negatively charged albumin does not pass through the glomerular kidney filter, primarily due to the presence of a high negative charge on the surface of the epithelial cells. This charge is due to the structure of phospholipids of cell membranes rich in polyene (polyunsaturated) fatty acids. The decrease in the number of double bonds in the acyl residues of phospholipids reduces the negative charge, and albumin begins to be filtered into the primary urine in an increased amount. All these changes occur in the development of atherosclerosis, so microalbuminuria develops in patients with hereditary forms of HLP, coronary heart disease (CHD), arterial hypertension, as well as in 10% of practically healthy people (in screening studies) and in patients with impaired glucose tolerance. Changes in the structure of phospholipids of plasma membranes of highly differentiated cells occur in atherosclerosis and immediately affect the charge of membranes, so a study on microalbuminuria can reveal early stages of the disease.

[1], [2], [3], [4], [5], [6], [7], [8], [9], [10]