Serum and urinary activities of beta-N-acetylglucosaminidase and beta-glucuronidase in diabetic patients

Prospective study of the enzymatic activities in urine of N-acetyl-beta-D-glucosaminidase, alpha-D-mannosidase, alpha- and beta-D-glucosidases, alpha-L- and beta-D-fucosidases, and beta-D-galactosidase in type I diabetes mellitus with early nephropathy

Different surveys have been carried out on the plasma activities of different glycosidases in patients with insulin-dependent diabetes mellitus, but research on urinary glycosidases in this disease is scanty and incomplete. To elucidate the behavior of these lysosomal enzymes in the metabolic alterations occurring in the glomerular basal membrane during the initial stages of diabetic nephropathy, we conducted a prospective study to examine the urinary activities of N-acetyl-beta-D-glucosaminidase (NAG), alpha-D-mannosidase, alpha- and beta-D-glucosidase, alpha-L- and beta-D-fucosidase, and beta-D-galactosidase in patients with type I insulin-dependent diabetes mellitus, surveyed over 18 months, whose early diabetic nephropathy was detected by the presence of microalbuminuria. The simultaneous determination of beta 2-microglobulin in urine confirmed the glomerular origin of the albuminuria. No statistically significant correlation was found between the levels of albuminuria and the activities of any of the glycosidases analyzed. In the diabetic patients, a significant decrease was observed in the activities of all the enzymes (p < 0.05), except NAG and alpha-D-mannosidase, although the decrease in the latter was very close to statistical significance (p = 0.028, unilateral; p = 0.057 bilateral). Similarly, in the patients, there was a significant negative correlation (p < 0.05) with the serum levels of fructosamine, except with beta-D-galactosidase, which showed a positive correlation (p < 0.05) with fructosamine and blood HbA1c.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased serum N-acetyl-beta-D-glucosaminidase and alpha-D-mannosidase activities in obese subjects

We have studied N-acetyl-beta-D-glucosaminidase and alpha-D-mannosidase activities in human sera from 35 control subjects, 47 normo- and hyperinsulinemic obese persons, and 12 diabetic patients after a fasting period of 12 h and at 30, 60, 90, and 120 min after an oral glucose overload. The results show a significantly higher activity of these 2 enzymes in obese subjects and diabetic patients, of similar magnitude, especially in those obese persons with a higher grade of obesity. Moreover, the activity of these glycosidases decreases in a similar way in all these 3 groups after the oral glucose overload.

Delay of progression of diabetic microangiopathy

Three muscle biopsies were performed in 53 overt type II diabetics over a period of approximately 2 years. At baseline, 21 (40%) had an abnormally increased capillary basement membrane width in muscle. Thirty-five subjects received glipizide and 18, placebo. At baseline, no statistically significant difference was found in the muscle capillary basement membrane width between the two groups (P = NS). In the subjects receiving placebo, the mean width of the muscle capillary basement membrane increased (P = NS), but in those receiving glipizide, the mean decreased from 193 +/- 13 nm (SEM) to 161 +/- 10 nm (P = .02). Fasting plasma glucose and glycosylated hemoglobin A1 significantly decreased (P less than .001) after two years in those receiving glipizide. In 15 subjects, mean glycosylated hemoglobin A1 reached the normal range, and mean muscle capillary basement membrane width decreased to a level close to that found in subjects without diabetes (P = NS). Determinations of enzyme activities involved in the synthesis and degradation of glycoproteins revealed a 2-year significant decrease of muscle glucosyltransferase (synthesis) activity (P less than .01) in the glipizide-treated subjects as opposed to a significant increase (P less than .001) in those receiving placebo. Muscle N-acetyl-beta-glucosaminidase activity (degradation) was statistically increased (P less than .001) in those subjects taking glipizide, but decreased in those taking placebo (P less than .001).

Behaviour of some lysosomal enzymes in the plasma of insulin dependent diabetic patients during artificial pancreas treatment

The plasma levels of three lysosomal enzymes, beta-D-N-acetylglucosaminidase, beta-D-glucuronidase, and alpha-L-fucosidase, were fluorimetrically determined in seven insulin-dependent diabetic patients one day before, one day after, and during a two-day treatment with the artificial pancreas, at 4 to 5 h intervals. A statistically significant decrease of the plasma level of each enzyme was observed during artificial pancreas treatment. The extent of decrease was 30 to 35% for beta-N-acetylglucosaminidase, 35 to 40% for beta-D-glucuronidase, and 20 to 25% for alpha-L-fucosidase. The decrease occurred earlier (at the first day of treatment) for beta-D-N-acetylglucosaminidase, and later (at the second day of treatment, and lasting to the first day after treatment) for the other two enzymes. These results suggest a direct connection between the lysosomal apparatus and insulin-controlled metabolic pathways, and a potential role for lysosomal enzymes as indicators of the metabolic compensation in diabetes.

Serum enzymes of lysosomal origin as indicators of the metabolic control in non-insulin-dependent diabetics

Several lysosomal enzymes (beta-N-acetyl-D-glucosaminidase, beta-D-glucuronidase, alpha-D-galactosidase, beta-D-galactosidase, alpha-D-glucosidase, beta-D-glucosidase, alpha-L-fucosidase and alpha-D-mannosidase) were determined in the serum of 54 non-insulin-dependent diabetics with different degrees of metabolic control and without complications and in 18 non-insulin-dependent diabetics with complications. The serum levels of beta-N-acetyl-D-glucosaminidase, beta-D-glucuronidase, alpha-D-galactosidase, and alpha-D-mannosidase were significantly (p less than 0.01) higher in the diabetics without complications. The levels of beta-N-acetyl-D-glucosaminidase and beta-D-glucuronidase were inversely proportional to the degree of metabolic control, in a statistically significant manner. Moreover the levels of these enzymes decreased to normal values during a 2-month period of controlled oral hypoglycemic drug-diet therapy resulting in metabolic compensation. The presence of complications was indicated by a further increase of serum beta-N-acetyl-D-glucosaminidase and beta-D-glucuronidase; however the portion of lysosomal enzyme activities due to complications remained unchanged after controlled therapy aimed at compensating the metabolism. The conclusion is drawn that in non-insulin-dependent diabetics, as already shown for insulin dependent-diabetics, serum lysosomal enzymes, especially beta-N-acetyl-D-glucosaminidase and beta-D-glucuronidase, are good intraindividual indicators of the metabolic control of the disease.

Correlation between urinary activity of N-acetyl-beta-D-glucosaminidase (NAG) and albumin excretion rate in type II (non-insulin-dependent) diabetic subjects

Different kidney diseases are often associated with high urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG), a lysosomal enzyme involved in the breakdown of glycoproteins, whose activity is also increased in diabetic patients with poor metabolic control or vascular complications. In order to evaluate the relationship between renal function and urinary NAG levels in diabetes mellitus, 30 type II diabetic patients without evidence of kidney disease and 18 control subjects were studied. In each subject 24-h urinary excretion rates of NAG (fluorimetric method), albumin and beta 2-microglobulin (radioimmunoassay), together with 51Cr-EDTA clearance were performed. In diabetic patients urinary levels of NAG (356 +/- 25 vs 162 +/- 9.2 nmol/h/mg creatinine, p less than 0.0001) and albumin (21 +/- 2.5 vs 4.3 +/- 0.5 mg/24h, p less than 0.0001) were significantly higher than in the controls, while beta 2-microglobulin levels and 51Cr-EDTA clearance did not differ in the two groups. Moreover in diabetic patients NAG and albumin levels were positively and significantly correlated (r = 0.63, p less than 0.001). These results suggest that urinary NAG excretion rate may be altered early in diabetic patients with apparently normal renal function; its diagnostic value seems to be similar to that of the albumin excretion rate.

Serum enzymes of lysosomal origin as indicators of the metabolic control in diabetes: comparison with glycated hemoglobin and albumin

Several lysosomal enzymes (beta-N-D-acetylglucosaminidase, beta-D-glucuronidase, alpha-D-galactosidase, beta-D-galactosidase, alpha-L-fucosidase, alpha-D-glucosidase, alpha-D-mannosidase, beta-D-glucosidase), glycated albumin and glycated hemoglobin (HbA1c) were determined in the serum of 81 insulin-dependent diabetics with different degrees of metabolic control (optimal, 21 patients; good, 39 patients; poor, 21 patients) and without signs of complications, and in 42 control subjects. All parameters examined increased in serum in inverse proportion to the degree of metabolic control. A highly significant correlation (p less than 0.01) was found between lysosomal enzymes and both glycated albumin and HbA1c. All parameters correlated with hyperglycemia, glycated albumin having the highest r-value (0.586) and lysosomal enzymes the lowest one. Unlike glycated albumin and HbA1c, serum levels of lysosomal enzymes in patients with optimal metabolic control were undistinguishable or even lower than those of controls. A 2-month longitudinal monitoring of a patient who was hospitalized in conditions of poor metabolic control and adequately treated, proved that lysosomal enzymes diminished in serum parallel to glycated albumin and HbA1c in relation to improvement of the metabolic situation. The conclusion is drawn that serum lysosomal enzymes are good indicators of the metabolic control of diabetic patients probably reflecting the overall metabolic state connected with insulin action rather than hyperglycemia.

Enzyme activities as a predictor of diabetic vasculopathy

Forty-one patients with chemical diabetes had three oral glucose tolerance tests and underwent muscle biopsy three times over a period of three years. Twenty-three received glipizide and 18 placebo. Those taking placebo had an increase in the mean muscle capillary basement membrane width (p = 0.01), but those taking glipizide showed a decrease (p = 0.01) to values no different from those of nondiabetic subjects. Determinations of enzyme activities involved in the synthesis and degradation of glycoproteins revealed a three-year decrease (not significant) in muscle glucosyltransferase activity in the glipizide-treated patients, but a statistically significant difference (p less than 0.01) comparing the adjusted means of the two treatment groups. N-acetyl-beta-glucosaminidase activity was significantly increased in muscle from baseline values (p less than 0.01), with adjusted means also significantly different (p less than 0.01). The data suggest that changes in basement membrane and enzyme activities are correlated, and the latter may be a predictor to follow the development, progression, or regression of diabetic vasculopathy.

Serum activity of beta-N-acetylglucosaminidase in obese hyperinsulinemic subjects

We have measured serum activity of beta-N-acetylglucosaminidase (NAG, fluorimetric method) in some groups of obese subjects with similar degrees of overweight but with different insulin secretion and glucose tolerance (GT) during OGTT. In the control group (35 normal subjects, mean body weight 102% of ideal body weight, normal GT) NAG was 282 +/- 77 nmol S/h/ml; in group I (11 subjects, body weight 149%, normal GT and insulin levels) NAG was 304 +/- 55; in group II (19 subjects, body weight 142%, normal GT and high insulin levels) NAG was 453 +/- 90 (p less than 0.001 vs group I and controls); in group III (14 subjects, body weight 154%, impaired GT and high insulin levels) NAG was 481 +/- 108 (p less than 0.005 vs group I and controls); in group IV (16 subjects, body weight 153%, diabetic GT and high insulin levels) NAG was 657 +/- 109 (p less than 0.001 vs other groups). Moreover in the whole series NAG levels and insulin areas, but not NAG levels and degree of overweight, were significantly correlated (r=0.46, p less than 0.001). These data show that hyperinsulinism (especially when there is also pathological glucose tolerance) can positively affect NAG levels, probably through altered glycoprotein turnover, of which NAG serum levels are a sensitive indicator.