Use of renal enzymes to evaluate nephrotoxicity in lithium treated patients

NAG level differences in panic disorder and agoraphobia

It is not clear if panic disorder (PD) and agoraphobia are variants of the same disorder or distinct diseases. A laboratory test could help resolve this issue. Research has shown that levels of the urinary lysosomal enzyme N-acetyl-beta-glusosaminidase (NAG) differ between patients with various psychiatric disorders. This study examined whether NAG levels would be similar in PD and agoraphobia, suggesting the two disorders may be the same disorder, or different, suggesting they may be distinct diseases. Differences found could suggest either qualitative or quantitative distinctions between these disorders. Ninety-one agoraphobics were compared to 24 patients with panic disorder. NAG levels were significantly lower in panic patients compared to agoraphobic patients 9.7+/- 8 versus 22+/- 21; P< .005. These data provide limited support for the hypothesis that PD and agoraphobia may be distinct diseases.

Lithium-induced renal toxicity in rats: protection by a novel antioxidant caffeic acid phenethyl ester

Lithium carbonate used in the long-term treatment of manic-depressive illness has been reported to lead to progressive renal impairment in rats and humans. Caffeic acid phenethyl ester (CAPE), a component of honeybee propolis, protects tissues from reactive oxygene species mediated oxidative stress in ischemia-reperfusion and toxic injuries. The beneficial effect CAPE on lithium-induced nephrotoxicity has not been reported yet. The purpose of this study was to examine a possible renoprotective effect of CAPE against lithium-induced nephrotoxicity in a rat model. Twenty-two adult male rats were randomly divided into three experimental groups, as follows: control group, lithium-treated group (Li), and lithium plus CAPE-treated group (Li+CAPE). Li were treated intraperitoneally (i.p.) with 25 mg/kg Li2CO3 solution in 0.9% NaCl twice daily for 4 weeks. CAPE was co-administered i.p. with a dose of 10 microM/kg/day for 4 weeks. Serum Li, blood urea nitrogen and plasma creatinine, urinary N-acetyl-beta-D-glucosaminidase (NAG, a marker of renal tubular injury), and malondialdehyde (MDA, an index of lipid peroxidation), were used as markers of oxidative stress-induced renal impairment in Li-treated rats. Superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities were studied to evaluate the changes of antioxidant status in renal tissue. Serum Li levels were found high in the Li and Li+CAPE groups. In Li-administrated rats, urinary NAG and renal MDA levels were increased according to control and Li+CAPE groups (p < 0.05). CAPE caused a significant reduction in the levels of these parameters. Likewise, renal SOD, CAT and GSH-Px activities were decreased in Li-administrated animals; CAPE caused a significant increase in the activities of these antioxidant enzymes. In conclusion, CAPE treatment has a protective effect against Li-induced renal tubular damage and oxidative stress in a rat model.

Increase by NO synthase inhibitor of lead-induced release of N-acetyl-beta-D-glucosaminidase from perfused rat kidney

Urinary N-acetyl-beta-D-glucosaminidase (NAG) had been shown to be a useful early marker of renal injury such as lead nephrotoxicity. This study investigated the effect of lead acetate on nephrotoxicity and its correlation with the nitric oxide (NO) system by determining the NAG release in perfused rat kidney. Lead acetate caused a time and concentration-dependent increase in enzymuria. The effect of concurrent perfusion with lead and L-arginine (L-arg) or L-N(G)-nitro arginine methyl ester (L-NAME) [substrate and inhibitor of NO synthase respectively] in the perfusion fluid was also studied by measuring NAG activity in the perfusate kidney rat. L-arg (2 mM) has significantly decreased the lead-induced NAG release (P < 0.001), and L-NAME (0.1 mM) has significantly increased the lead-induced enzyme release in a time-dependent manner (P < 0.001). Moreover, histological studies using light microscope showed that some of the epithelial cells of the proximal convoluted tubules are degenerated or necrotic and desquamated into the lumens in rat treated with lead acetate. This change occurs at 50 microg/dl of lead acetate and was increased by addition of L-NAME to lead acetate. However, addition of L-arg had no effect on histology of lead nephrotoxicity. This may suggest that lead may interfere with the NO system in rat kidney.

An association of NAG levels and a mutation of the CCK gene in panic disorder patients

Levels of the enzyme N-acetyl-beta-glucosaminidase (NAG) and a mutation of cholecystokinin (CCK) gene appear to be independently associated with panic disorder. We explored whether there was an association of NAG levels and a CCK mutation identified in a group of panic disorder patients. NAG was measured in 12 panic disorder patients who had a mutation of the CCK gene and 17 who did not. Urine for NAG was collected at baseline and after 3 and 6 weeks of treatment. NAG levels were lower at all three times in the patients that did not have the CCK mutation. The difference between the two groups was significant at week 6 (P < 0.02), and showed a trend toward a difference at baseline (P < 0.15).

Inhibition by lithium and rubidium of gentamicin-induced release of N-acetyl-beta-D-glucosaminidase from perfused rat kidney

N-acetyl-beta-D-glucosaminidase (NAG) is one of the sensitive hydrolytic lysosomal enzymes which is released after renal tubular damages. We studied gentamicin-induced nephrotoxicity by determining the NAG release in perfused rat kidney. 100 micrograms/ml of gentamicin caused a time-dependent increase in enzymuria, peaking at 90 min. At this time the released NAG is about sixfold more than the control. The effect of concurrent perfusion with 100 micrograms/ml gentamicin and with 0.5 mmol/l lithium chloride or 0.5 mmol/l rubidium chloride in the perfusion fluid was also studied by measuring NAG activity in the perfusate. Both cations decrease the gentamicin-induced NAG release. However, the inhibitory effect of lithium chloride may be due to interference of this ion with the polyphosphoinositide cycle in renal tubular lysosomal membranes. There is no obvious evidence for an inhibitory effect of rubidium chloride.

Association of levels of N-acetyl-beta-glucosaminidase with severity of psychiatric symptoms in panic disorder

Urinary levels of N-acetyl-beta-glucosaminidase (NAG) were measured in 58 patients with panic disorder. NAG levels were found to be significantly related to the severity of 23 of 72 mood states, measured by the Profile of Mood States, which were grouped in three categories: hostility or irritability, sadness, and panic. A similar result was found in a previous study of bipolar patients. NAG levels were also related to scores on the Hamilton Rating Scale for Anxiety and the Sheehan Patient-Rated Anxiety Scale. It is speculated that NAG could be a marker for serotonin.

Association of levels of N-acetyl-beta-glucosaminidase with specific psychiatric symptoms in bipolar patients

The levels of N-acetyl-beta-glucosaminidase (NAG) in urine from 35 patients with bipolar affective disorder were compared with scores for the 90 items (symptoms) of the Symptom Checklist (SCL-90). There were significant negative correlations between NAG levels and 23 of the SCL-90 variables (symptoms). These symptoms could be grouped into the following categories: anxiety, unusual or psychotic thinking, suicidal thinking, dysphoria, irritability, nausea, headaches, memory problems, and loss of interest. Serotonin abnormalities may play a role in the production of many of these symptoms. The hypothesis that NAG could be a marker for a serotonin activity is discussed.

Elevated levels of N-acetyl-beta-glucosaminidase in affective disorders and chemical dependence

Levels of N-acetyl-beta-glucosaminidase (NAG) were examined in 575 patients with various psychiatric diagnoses and 38 non-ill controls. Ten percent of affectively disordered patients and 19% of chemically dependent patients had abnormal NAG levels, whereas none of the 38 controls did (P less than 0.05 and P less than 0.003 respectively). Other psychiatric diagnostic groups were not associated with abnormal levels of this enzyme.

New applications of lithium therapy

Several placebo-controlled double-blind studies have indicated that lithium sometimes augments antidepressants, converting nonresponding patients to responders. Lithium therapy has also benefitted some schizoaffective patients and some alcoholics. Side effects are minimal. Mechanisms involved in lithium's effectiveness have not yet been discovered.

Elevation of the renal enzyme N-acetyl-beta-glucosaminidase in affectively disordered patients

A minority of patients with affective disorders experience mild elevations of the renal enzyme N-acetyl-beta-glucosaminidase (NAG). Some affectively disordered patients also have reduced concentrating ability and reduced creatinine clearance. Thirty-one affectively disordered patients were compared to 17 healthy controls, to evaluate whether these various renal abnormalities are associated with one another and to further examine the proportion of affectively disordered patients experiencing NAG elevations. Twenty-nine percent of patients had an elevated NAG, whereas none of the controls did (P less than .005). There was a trend for an association between elevated NAGs and reduced creatinine clearance (P less than .08), but no association was found between concentrating ability and either elevated NAG or reduced creatinine clearance.

Neuroleptics, lithium and renal function

Renal function test results in 26 patients on neuroleptic treatment, who had never received lithium or antidepressants, were compared with those in a matched group, treated with lithium; also, their tubular response to DDAVP was compared with that of 25 control subjects. Measurements of serum creatinine, creatinine clearance, and urinary albumin excretion showed no abnormality attributable to either neuroleptics or lithium. The maximum urine concentrating ability after DDAVP was significantly lower in the neuroleptic group than in controls, but significantly higher than in the lithium-treated patients. There was a significant correlation between excretion of urinary beta 2-microglobulin and duration of neuroleptic treatment, but mean excretion rates were the same in both treatment groups. The results suggest that neuroleptics as well as lithium impair urine concentrating ability.