Analysis of the Structure-Function-Dynamics Relationships of GALT Enzyme and of Its Pathogenic Mutant p.Q188R: A Molecular Dynamics Simulation Study in Different Experimental Conditions

The third step of the catabolism of galactose in mammals is catalyzed by the enzyme galactose-1-phosphate uridylyltransferase (GALT), a homodimeric enzyme with two active sites located in the proximity of the intersubunit interface. Mutations of this enzyme are associated to the rare inborn error of metabolism known as classic galactosemia; in particular, the most common mutation, associated with the most severe phenotype, is the one that replaces Gln188 in the active site of the enzyme with Arg (p.Gln188Arg). In the past, and more recently, the structural effects of this mutation were deduced on the static structure of the wild-type human enzyme; however, we feel that a dynamic view of the proteins is necessary to deeply understand their behavior and obtain tips for possible therapeutic interventions. Thus, we performed molecular dynamics simulations of both wild-type and p.Gln188Arg GALT proteins in the absence or in the presence of the substrates in different conditions of temperature. Our results suggest the importance of the intersubunit interactions for a correct activity of this enzyme and can be used as a starting point for the search of drugs able to rescue the activity of this enzyme in galactosemic patients.

Neuroradiologic Phenotyping of Galactosemia: From the Neonatal Form to the Chronic Stage

Galactosemia is a rare genetic condition caused by mutation of enzymes involved in galactose and glucose metabolism. The varying clinical spectrum reflects the genetic complexity of this entity manifesting as acute neonatal toxicity syndrome, requiring prompt diagnosis and treatment, to more insidious clinical scenarios as observed in the subacute and chronic presentations. The current literature predominantly focuses on the long-standing sequelae of this disease. The purpose of this multicenter clinical report comprising 17 patients with galactosemia is to highlight the MR imaging patterns encompassing the whole spectrum of galactosemia, emphasizing the 3 main clinical subtypes: 1) acute neonatal presentation, with predominant white matter edema; 2) subacute clinical onset with a new finding called the "double cap sign"; and 3) a chronic phase of the disease with heterogeneous imaging findings. The knowledge of these different patterns together with MR spectroscopy and the clinical presentation may help in prioritizing galactosemia over other neonatal metabolic diseases and prevent possible complications.

Gray and white matter are both affected in classical galactosemia: An explorative study on the association between neuroimaging and clinical outcome

BACKGROUND

Classical Galactosemia (CG) is an inherited disorder of galactose metabolism caused by a deficiency of the galactose-1-phosphate uridylyltransferase (GALT) enzyme resulting in neurocognitive complications. As in many Inborn Errors of Metabolism, the metabolic pathway of CG is well-defined, but the pathophysiology and high variability in clinical outcome are poorly understood. The aim of this study was to investigate structural changes of the brain of CG patients on MRI and their association with clinical outcome.

METHODS

In this prospective cohort study an MRI protocol was developed to evaluate gray matter (GM) and white matter (WM) volume of the cerebrum and cerebellum, WM hyperintensity volume, WM microstructure and myelin content with the use of conventional MRI techniques, diffusion tensor imaging (DTI) and quantitative T1 mapping. The association between several neuroimaging parameters and both neurological and intellectual outcome was investigated.

RESULTS

Twenty-one patients with CG (median age 22 years, range 8-47) and 24 controls (median age 30, range 16-52) were included. Compared to controls, the WM of CG patients was lower in volume and the microstructure of WM was impaired both in the whole brain and corticospinal tract (CST) and the lower R1 values of WM, GM and the CST were indicative of less myelin. The volume of WM lesions were comparable between patients and controls. The 9/16 patients with a poor neurological outcome (defined as the presence of a tremor and/or dystonia), demonstrated a lower WM volume, an impaired WM microstructure and lower R1 values of the WM indicative of less myelin content compared to 7/16 patients without movement disorders. In 15/21 patients with a poor intellectual outcome (defined as an IQ < 85) both GM and WM were affected with a lower cerebral and cerebellar WM and GM volume compared to 6/21 patients with an IQ ≥ 85. Both the severity of the tremor (as indicated by the Tremor Rating Scale) and IQ (as continuous measure) were associated with several neuroimaging parameters such as GM volume, WM volume, CSF volume, WM microstructure parameters and R1 values of GM and WM.

CONCLUSION

In this explorative study performed in patients with Classical Galactosemia, not only WM but also GM pathology was found, with more severe brain abnormalities on MRI in patients with a poor neurological and intellectual outcome. The finding that structural changes of the brain were associated with the severity of long-term complications indicates that quantitative MRI techniques could be of use to explain neurological and cognitive dysfunction as part of the disease spectrum. Based on the clinical outcome of patients, the absence of widespread WM lesions and the finding that both GM and WM are affected, CG could be primarily a GM disease with secondary damage to the WM as a result of neuronal degeneration. To investigate this further the course of GM and WM should be evaluated in longitudinal research, which could also clarify if CG is a neurodegenerative disease.

Identification of neuronal structures and pathways corresponding to clinical functioning in galactosemia

Classic galactosemia (OMIM# 230400) is an autosomal recessive disorder due to galactose-1-phosphate uridyltransferase deficiency. Newborn screening and prompt treatment with a galactose-free diet prevent the severe consequences of galactosemia, but clinical outcomes remain suboptimal. Five men and five women with classic galactosemia (mean age = 27.2 ± 5.47 years) received comprehensive neurological and neuropsychological evaluations, electroencephalogram (EEG) and magnetic resonance imaging (MRI). MRI data from nine healthy controls (mean age = 30.22 ± 3.52 years) were used for comparison measures. Galactosemia subjects experienced impaired memory, language processing, visual-motor skills, and increased anxiety. Neurological examinations revealed tremor and dysarthria in six subjects. In addition, there was ataxia in three subjects and six subjects had abnormal gait. Mean full scale IQ was 80.4 ± 17.3. EEG evaluations revealed right-sided abnormalities in five subjects and bilateral abnormalities in one subject. Compared to age- and gender-matched controls, subjects with galactosemia had reduced volume in left cerebellum white matter, bilateral putamen, and left superior temporal sulcus. Galactosemia patients also had lower fractional anisotropy and higher radial diffusivity values in the dorsal and ventral language networks compared to the controls. Furthermore, there were significant correlations between neuropsychological test results and the T1 volume and diffusivity scalars. Our findings help to identify anatomic correlates to motor control, learning and memory, and language in subjects with galactosemia. The results from this preliminary assessment may provide insights into the pathophysiology of this inborn error of metabolism.

Receptor-mediated attenuation of insulin-like growth factor-1 activity by galactose-1-phosphate in neonate skin fibroblast cultures: Galactosemia pathogenesis

BACKGROUND

The pathogenesis of classical galactosemia, a rare metabolic disorder associated with developmental complications in neonates and children due to inherited deficiency of galactose-1-phosphate (Gal-1-P) uridylyltransferase (GALT), is known to be mediated by elevated Gal-1-P levels and involves a cascade of cytokines, reactive oxygen species (ROS) and growth factors.

OBJECTIVES

To examine ex vivo the effect of Gal-1-P on the mitogenic activity of different growth factors, particularly insulin-like growth factor-1 (IGF-1), known to regulate growth and development from the fetal stage to adulthood.

MATERIAL AND METHODS

Fibroblasts derived from the foreskin of 3-8-day-old healthy neonates were cultured for 1-14 days with 0-20 mM galactose or 0-10 mM Gal-1-P and then stimulated with 5% fetal bovine serum (FBS) or 50 ng/mL of platelet-derived growth factor (PDGF) or fibroblast growth factor (FGF) or IGF-1 for 24 h. DNA synthesis was measured and protein expression of PDGFR, FGFR and IGF-1R was assessed with western blotting.

RESULTS

Supra-physiological concentrations of galactose significantly decreased FBSand IGF-1-induced BrdU incorporation. The presence of Gal-1-P (5-10 mM) in culture medium for 7-14 days significantly (p < 0.01) decreased IGF-1-, PDGFand FBS-stimulated DNA synthesis. While treatment with Gal-1-P selectively and significantly (p < 0.01) reduced the protein expression of IGF-1 receptor, galactose treatment did not have any marked effect on examined growth factor receptors.

CONCLUSIONS

This study demonstrates that Gal-1-P impairs IGF-1 activity through IGF-1-receptor impairment, thereby providing a new insight into the molecular mechanisms of galactosemia pathogenesis.

Novel mRNA-Based Therapy Reduces Toxic Galactose Metabolites and Overcomes Galactose Sensitivity in a Mouse Model of Classic Galactosemia

Classic galactosemia (CG) is a potentially lethal inborn error of galactose metabolism that results from deleterious mutations in the human galactose-1 phosphate uridylyltransferase (GALT) gene. Previously, we constructed a GalT^-/- (GalT-deficient) mouse model that exhibits galactose sensitivity in the newborn mutant pups, reduced fertility in adult females, impaired motor functions, and growth restriction in both sexes. In this study, we tested whether restoration of hepatic GALT activity alone could decrease galactose-1 phosphate (gal-1P) and plasma galactose in the mouse model. The administration of different doses of mouse GalT (mGalT) mRNA resulted in a dose-dependent increase in mGalT protein expression and enzyme activity in the liver of GalT-deficient mice. Single intravenous (i.v.) dose of human GALT (hGALT) mRNA decreased gal-1P in mutant mouse liver and red blood cells (RBCs) within 24 h with low levels maintained for over a week. Repeated i.v. injections increased hepatic GalT expression, nearly normalized gal-1P levels in liver, and decreased gal-1P levels in RBCs and peripheral tissues throughout all doses. Moreover, repeated dosing reduced plasma galactose by 60% or more throughout all four doses. Additionally, a single intraperitoneal dose of hGALT mRNA overcame the galactose sensitivity and promoted the growth in a GalT^-/- newborn pup.

Effect of genotype on galactose-1-phosphate in classic galactosemia patients

Impaired activity of galactose-1-phosphate uridyltransferase (GALT) causes classic galactosemia (OMIM 230400), characterized by the accumulation of galactose-1-phosphate (GAL1P) in patients' red blood cells (RBCs). Our recent study demonstrated a correlation between RBC GAL1P and long-term outcomes in galactosemia patients. Here, we analyze biochemical and molecular results in 77 classic galactosemia patients to evaluate the association between GALT genotypes and GAL1P concentration in RBCs. Experimental data from model organisms were also included to assess the correlation between GAL1P and predicted residual activity of each genotype. Although all individuals in this study showed markedly reduced RBC GALT activity, we observed significant differences in RBC GAL1P concentrations among galactosemia genotypes. While levels of GAL1P on treatment did not correlate with RBC GALT activities (p = 0.166), there was a negative nonlinear correlation between mean GAL1P concentrations and predicted residual enzyme activity of genotype (p = 0.004). These studies suggest that GAL1P levels in RBCs on treatment likely reflect the overall functional impairment of GALT in patients with galactosemia.

Evidence of oxidative stress in brain and liver of young rats submitted to experimental galactosemia

Galactosemia is a disorder of galactose metabolism, leading to the accumulation of this carbohydrate. Galactosemic patients present brain and liver damage. For evaluated oxidative stress, 30-day-old males Wistar rats were divided into two groups: galactose group, that received a single injection of this carbohydrate (5 μmol/g), and control group, that received saline 0.9 % in the same conditions. One, twelve or twenty-four hours after the administration, animals were euthanized and cerebral cortex, cerebellum, and liver were isolated. After one hour, it was found a significant increase in TBA-RS levels, nitrate and nitrite and protein carbonyl contents in cerebral cortex, as well as protein carbonyl content in the cerebellum and in hepatic level of TBA-RS, and a significant decrease in nitrate and nitrite contents in cerebellum. TBA-RS levels were also found increased in all studied tissues, as well as nitrate and nitrite contents in cerebral cortex and cerebellum, that also present increased protein carbonyl content and impairments in the activity of antioxidant enzymes of rats euthanized at twelve hours. Finally, animals euthanized after twenty-four hours present an increase of TBA-RS levels in studied tissues, as well as the protein carbonyl content in cerebellum and liver. These animals also present an increased nitrate and nitrite content and impairment of antioxidant enzymes activities. Taken together, our data suggest that acute galactose administration impairs redox homeostasis in brain and liver of rats.

Oxidative Stress in Rats After 60 Days of Hypergalactosemia or Hyperglycemia

Two of the models used in current diabetes research include the hypergalactosemic rat and the hyperglucosemic, streptozotocin-induced diabetic rat. Few studies, however, have examined the concurrence of these two models regarding the effects of elevated hexoses on biomarkers of oxidative stress. This study compared the activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase and the concentrations of glutathione, glutathione disulfide, and thiobarbituric acid reactants (as a measure of lipid peroxidation) in liver, kidney, and heart of Sprague-Dawley rats after 60 days of either a 50% galactose diet or insulin deficiency caused by streptozotocin injection. Most rats from both models developed bilateral cataracts. Blood glucose and glycosy-lated hemoglobin A1c concentrations were elevated in streptozotocin diabetic rats. Streptozotocin diabetic rats exhibited elevated activities of renal superoxide dismutase, cardiac catalase, and renal and cardiac glutathione peroxidase, as well as elevated hepatic lipid peroxidation. Insulin treatment of streptozotocin-induced diabetic rats normalized altered markers. In galactosemic rats, hepatic lipid peroxidation was increased whereas glutathione reductase activity was diminished. Glutathione levels in liver were decreased in diabetic rats but elevated in the galactosemic rats, whereas hepatic glutathione disulfide concentrations were decreased much more in diabetes than in galactosemia. Insulin treatment reversed/prevented all changes caused by streptozotocin-induced diabetes. Lack of concomitance in these data indicate that the 60-day galactose-fed rat is not experiencing the same oxidative stress as the streptozotocin diabetic rat, and that investigators must be cautious drawing conclusions regarding the concurrence of the effects of the two animal models on oxidative stress biomarkers.

Grey matter density decreases as well as increases in patients with classic galactosemia: A voxel-based morphometry study

Brain impairments have been observed in patients with classic galactosemia, an inherited metabolic disorder resulting in a particular neuro-cognitive profile. Neuroimaging studies showed abnormalities such as diffuse white mater (WM) abnormalities and grey matter (GM) atrophy. Our current study analysed grey matter density using voxel-based morphometry (VBM) and compared the brains of eight adolescent patients with classic galactosemia with eight healthy gender- and aged-matched controls. GM density differences were found in several regions. Decreased GM density was found in the patients in the bilateral putamen and bilateral occipital cortex. Increased GM density in the patients, on the other hand, was found in the bilateral inferior frontal and medial prefrontal cortex. The anatomical profile of the abnormalities is in line with the neuro-cognitive profile of patients with classic galactosemia, including motor dysfunction, speech and language difficulties and higher order cognitive problems. Less favourable GM densities in patients (either increased or decreased compared to controls) correlated with younger age, a worse visual working memory performance, and an older age at initiation of the galactose-restricted diet. To conclude, this explorative study is the first to analyse the GM using VBM in this population, and demonstrates a mixed profile of both increased and decreased GM density in these patients.

The Rapid and Sensitive Quantitative Determination of Galactose by Combined Enzymatic and Colorimetric Method: Application in Neonatal Screening

The quantitative measurement of galactose in blood is essential for the early diagnosis, treatment, and dietary monitoring of galactosemia patients. In this communication, we aimed to develop a rapid, sensitive, and cost-effective combined method for galactose determination in dry blood spots. This procedure was based on the combination of enzymatic reactions of galactose dehydrogenase (GalDH), dihydrolipoyl dehydrogenase (DLD), and alkaline phosphates with a colorimetric system. The incubation time and the concentration of enzymes used in new method were also optimized. The analytical performance was studied by the precision, recovery, linearity, and sensitivity parameters. Statistical analysis was applied to method comparison experiment. The regression equation and correlation coefficient (R (2)) were Y = 0.0085x + 0.032 and R (2) = 0.998, respectively. This assay exhibited a recovery in the range of 91.7-114.3 % and had the limit detection of 0.5 mg/dl for galactose. The between-run coefficient of variation (CV) was between 2.6 and 11.1 %. The within-run CV was between 4.9 and 9.2 %. Our results indicated that the new and reference methods were in agreement because no significant biases exist between them. Briefly, a quick and reliable combined enzymatic and colorimetric assay was presented for application in newborn mass screening and monitoring of galactosemia patients.

Galactose-1 phosphate uridylyltransferase (GalT) gene: A novel positive regulator of the PI3K/Akt signaling pathway in mouse fibroblasts

The vital importance of the Leloir pathway of galactose metabolism has been repeatedly demonstrated by various uni-/multicellular model organisms, as well human patients who have inherited deficiencies of the key GAL enzymes. Yet, other than the obvious links to the glycolytic pathway and glycan biosynthetic pathways, little is known about how this metabolic pathway interacts with the rest of the metabolic and signaling networks. In this study, we compared the growth and the expression levels of the key components of the PI3K/Akt growth signaling pathway in primary fibroblasts derived from normal and galactose-1 phosphate uridylyltransferase (GalT)-deficient mice, the latter exhibited a subfertility phenotype in adult females and growth restriction in both sexes. The growth potential and the protein levels of the pAkt(Thr308), pAkt(Ser473), pan-Akt, pPdk1, and Hsp90 proteins were significantly reduced by 62.5%, 60.3%, 66%, 66%, and 50%, respectively in the GalT-deficient cells. Reduced expression of phosphorylated Akt proteins in the mutant cells led to diminished phosphorylation of Gsk-3β (-74%). Protein expression of BiP and pPten were 276% and 176% higher respectively in cells with GalT-deficiency. Of the 24 genes interrogated using QIAGEN RT(2) Profiler PCR Custom Arrays, the mRNA abundance of Akt1, Pdpk1, Hsp90aa1 and Pi3kca genes were significantly reduced at least 2.03-, 1.37-, 2.45-, and 1.78-fold respectively in mutant fibroblasts. Both serum-fasted normal and GalT-deficient cells responded to Igf-1-induced activation of Akt phosphorylation at +15 min, but the mutant cells have lower phosphorylation levels. The steady-state protein abundance of Igf-1 receptor was also significantly reduced in mutant cells. Our results thus demonstrated that GalT deficiency can effect down-regulation of the PI3K/Akt growth signaling pathway in mouse fibroblasts through distinct mechanisms targeting both gene and protein expression levels.

White matter microstructure pathology in classic galactosemia revealed by neurite orientation dispersion and density imaging

White matter abnormalities have been observed in patients with classic galactosemia, an inborn error of galactose metabolism. However, magnetic resonance imaging (MRI) data collected in the past were generally qualitative in nature. Our objective was to investigate white matter microstructure pathology and examine correlations with outcome and behaviour in this disease, by using multi-shell diffusion weighted imaging. In addition to standard diffusion tensor imaging (DTI), neurite orientation dispersion and density imaging (NODDI) was used to estimate density and orientation dispersion of neurites in a group of eight patients (aged 16-21 years) and eight healthy controls (aged 15-20 years). Extensive white matter abnormalities were found: neurite density index (NDI) was lower in the patient group in bilateral anterior areas, and orientation dispersion index (ODI) was increased mainly in the left hemisphere. These specific regional profiles are in agreement with the cognitive profile observed in galactosemia, showing higher order cognitive impairments, and language and motor impairments, respectively. Less favourable white matter properties correlated positively with age and age at onset of diet, and negatively with behavioural outcome (e.g. visual working memory). To conclude, this study provides evidence of white matter pathology regarding density and dispersion of neurites in these patients. The results are discussed in light of suggested pathophysiological mechanisms.

Fertility preservation in female classic galactosemia patients

Almost every female classic galactosemia patient develops primary ovarian insufficiency (POI) as a diet-independent complication of the disease. This is a major concern for patients and their parents, and physicians are often asked about possible options to preserve fertility. Unfortunately, there are no recommendations on fertility preservation in this group. The unique pathophysiology of classic galactosemia with a severely reduced follicle pool at an early age requires an adjusted approach. In this article recommendations for physicians based on current knowledge concerning galactosemia and fertility preservation are made. Fertility preservation is only likely to be successful in very young prepubertal patients. In this group, cryopreservation of ovarian tissue is currently the only available technique. However, this technique is not ready for clinical application, it is considered experimental and reduces the ovarian reserve. Fertility preservation at an early age also raises ethical questions that should be taken into account. In addition, spontaneous conception despite POI is well described in classic galactosemia. The uncertainty surrounding fertility preservation and the significant chance of spontaneous pregnancy warrant counseling towards conservative application of these techniques. We propose that fertility preservation should only be offered with appropriate institutional research ethics approval to classic galactosemia girls at a young prepubertal age.

Modifiers of ovarian function in girls and women with classic galactosemia

CONTEXT

Classic galactosemia is a potentially lethal genetic disorder resulting from profound impairment of galactose-1P uridylyltransferase (GALT). More than 80% of girls and women with classic galactosemia experience primary or premature ovarian insufficiency despite neonatal diagnosis and rigorous lifelong dietary galactose restriction.

OBJECTIVE

The goal of this study was to test the relationship between markers of ovarian reserve, cryptic residual GALT activity, and spontaneous pubertal development in girls with classic galactosemia.

DESIGN AND SETTING

This was a cross-sectional study with some longitudinal follow-up in a university research environment.

PATIENTS

Patients included girls and women with classic galactosemia and unaffected controls, <1 month to 30 years old.

MAIN OUTCOME MEASURES

We evaluated plasma anti-Müllerian hormone (AMH) and FSH levels, antral follicle counts ascertained by ultrasound, and ovarian function as indicated by spontaneous vs assisted menarche.

RESULTS

More than 73% of the pre- and postpubertal girls and women with classic galactosemia in this study, ages >3 months to 30 years, demonstrated AMH levels below the 95% confidence interval for AMH among controls of the same age, and both pre- and postpubertal girls and women with classic galactosemia also demonstrated abnormally low antral follicle counts relative to age-matched controls. Predicted residual GALT activity ≥ 0.4% significantly increased the likelihood that a girl with classic galactosemia would demonstrate an AMH level ≥ 0.1 ng/mL.

CONCLUSIONS

A majority of girls with classic galactosemia demonstrate evidence of diminished ovarian reserve by 3 months of age, and predicted cryptic residual GALT activity is a modifier of ovarian function in galactosemic girls and women.

[A case of neonatal galactosemia]

The paper describes a rare case of hereditary thesaurismosis, galactosemia, in a full-term neonate girl aged 12 days with morphologically verified fetal giant-cell cholestatic hepatitis with the development of ascitis and jaundice.

Classic galactosemia presenting with unilateral Peters' anomaly

OBJECTIVE

To report a case of classic galactosemia that presented with a rare ocular finding, Peters' anomaly.

CLINICAL PRESENTATION AND INTERVENTION

A neonate, born to first-degree healthy cousins, presented with persistent vomiting, failure to thrive, lethargy, and jaundice. Corneal opacity was noticed in the left eye. Hydration and empiric antibiotics were started after collection of the required blood work, which included both a septic and a metabolic workup. A deficiency in erythrocyte galactose-1-phosphate uridyltransferase was found, and this led to the diagnosis of classic galactosemia and the elimination of galactose from the diet. Furthermore, a diagnosis of left unilateral Peters' anomaly was made after examination by a pediatric ophthalmologist. The patient was discharged in stable condition and follow-up visits were scheduled with the metabolic clinic, a dietician, and the pediatric ophthalmologist.

CONCLUSION

This was a case of classic galactosemia presenting with Peters' anomaly, probably due to autosomal recessive disorder from first-degree consanguinity marriage.

Proposal for the prevention of osteoporosis in paediatric patients with classical galactosaemia

Decreased bone mass in early childhood is an increasingly recognized problem in classical galactosaemia as in many other chronic diseases. Peak bone mass is reached in late adolescence; thus, increasing peak bone mass in childhood can prevent osteoporosis. Regular bone mass measurements and preventive treatment should begin in childhood. In the absence of evidence-based guidelines for identification and treatment of decreased bone mass in children, we provide a proposal based on our experience and the available literature. Dual-energy x-ray absorptiometry (DXA) should be used for bone mass assessment. Because cooperation is required, measurements can usually be performed from the age of 4 years. Interpretation of bone mass measurements is crucial for the diagnosis of osteopenia or osteoporosis. In children and adolescents, total body bone mineral content (BMC) as well as lean tissue mass (LTM) should be measured. Comparison of BMC corrected for LTM of the patient with the BMC corrected for LTM of healthy controls allows correction for the confounding effect of bone size. DXA should be repeated every two years in case of normal BMC, as this is the time window in which abnormalities become measurable. If BMC is between 0 and -1 SD, lifestyle factors such as physical activity, intake of calcium and vitamins K and D and oestrogen supplementation (in girls) should be optimized. If BMC is below -1 SD, we advise to start with supplementation of calcium, vitamin K(1) and vitamin D(3). DXA should be repeated yearly in case of BMC below 0 SD in order to identify deteriorations and improvements early.

Akt activation and augmented fibronectin production in hyperhexosemia

Dysmetabolic state in diabetes may lead to augmented synthesis of extracellular matrix (ECM) proteins. In the endothelial cells, we have previously demonstrated that glucose-induced fibronectin (FN) production and that of its splice variant, EDB(+)FN, is regulated by protein kinase B (PKB, also known as Akt). In this study, we investigated the role of Akt1 in ECM protein production in the organs affected by chronic diabetic complications. We studied Akt1/PKBalpha knockout mice and wild-type control littermates. To avoid confounding effects of systemic insulin, we used 30% galactose feeding to induce hyperhexosemia for 8 wk starting at 6 wk of age. We investigated FN mRNA, EDB(+)FN mRNA, and transforming growth factor (TGF)-beta mRNA expression, Akt phosphorylation, Akt kinase activity, and NF-kappaB and AP-1 activation in the retina, heart, and kidney. Renal and cardiac tissues were histologically examined. Galactose feeding caused significant upregulation of FN, EDB(+)FN, and TGF-beta in all tissues. FN protein levels paralleled mRNA. Such upregulation were prevented in Akt1-deficient galactose-fed mice. Galactose feeding caused ECM protein deposition in the glomeruli and in the myocardium, which was prevented in the Akt knockout mice. NF-kappaB and AP-1 activation was pronounced in galactose-fed wild-type mice and prevented in the galactose-fed Akt1/PKBalpha-deficient group. In the retina and kidney, Ser473 was the predominant site for Akt phosphorylation, whereas in the heart it was Thr308. Parallel experiment in streptozotocin-induced diabetic animals showed similar results. The data from this study indicate that hyperhexosemia-induced Akt/PKB activation may be an important mechanism leading to NF-kappaB and AP-1 activation and increased ECM protein synthesis in the organs affected by chronic diabetic complications.

Involvement of endoplasmic reticulum stress in a novel Classic Galactosemia model

Inherited deficiency of galactose-1-phosphate uridyltransferase (GALT) activity in humans leads to a potentially lethal disorder called Classic Galactosemia. It is well known that patients often accumulate high levels of galactose metabolites such as galactose-1-phosphate (gal-1-p) in their tissues. However, specific targets of gal-1-p and other accumulated metabolites remain uncertain. In this study, we developed a new model system to study this toxicity using primary fibroblasts derived from galactosemic patients. GALT activity was reconstituted in these primary cells through lentivirus-mediated gene transfer. Gene expression profiling showed that GALT-deficient cells, but not normal cells, responded to galactose challenge by activating a set of genes characteristic of endoplasmic reticulum (ER) stress. Western blot analysis showed that the master regulator of ER stress, BiP, was up-regulated at least threefold in these cells upon galactose challenge. We also found that treatment of these cells with galactose, but not glucose or hexose-free media reduced Ca2+ mobilization in response to activation of Gq-coupled receptors. To explore whether the muted Ca2+ mobilization is related to reduced inositol turnover, we discovered that gal-1-p competitively inhibited human inositol monophosphatase (hIMPase1). We hypothesize that galactose intoxication under GALT-deficiency resulted from accumulation of toxic galactose metabolite products, which led to the accumulation of unfolded proteins, altered calcium homeostasis, and subsequently ER stress.

Pregnancy and lactation in a woman with classical galactosaemia heterozygous for p.Q188R and p.R333W

A 31-year old patient who is compound heterozygous for the two galactose-1-phosphate uridyltransferase mutations p.Q188R and p.R333W delivered two healthy boys after uneventful spontaneous pregnancies. The patient chose to breast-feed her first baby and her galactose metabolites in blood and urine were monitored closely. A temporary increase in her galactose-1-phosphate (gal-1-P) levels with a maximum of 0.30 mmol/L on day 2 after delivery was observed. Galactose-1-phosphate was normalized 10 days after delivery. At the time of weaning, 8 months after delivery, her menses returned and she had normal sex steroid levels. She became pregnant again 2 months later. The second baby was also breast-fed. This time an increase in her gal-1-P values could be seen for 3 weeks with a maximum gal-1-P level of of 0.25 mmol/L at day 7. Only minor changes in her urine galactitol values were noted during the study period but the values stayed in the range of treated galactosaemia patients. We thus report that breast-feeding has been possible with only small adverse effects on the levels of galactose metabolites in a patient with classical galactosaemia.

Untreated classical galactosemia patient with mild phenotype

Despite life-long galactose restriction, long-term complications generally occur in classical galactosemia. We report an adult male with classical galactosemia (Q188R homozygosity, severely reduced erythrocyte galactose-1-phosphate uridyltransferase activity) who has a surprisingly mild phenotype despite genotype and enzyme activity associated with severe phenotype. Moreover he has a normal galactose intake from the age of 3 years. This case is probably an example of the important role of yet unknown susceptibility and or modifier genes.

Aqueous flow in galactose-fed dogs

Dogs fed galactose develop diabetes-like ocular complications that include keratopathy, cataracts, and retinopathy. The purpose of this study was to investigate whether galactosemic dogs display reduced aqueous flow similar to that observed in patients with insulin-dependent diabetes mellitus. Twelve male beagles at 9 months of age were divided into three groups of four. The Galactose group was fed diet containing 30% galactose for 97 months and the Reversal group was fed the galactose diet for an initial 38 months then standard dog diet for the remaining period. The Control group was fed standard dog diet for 97 months. Aqueous flow was determined by fluorophotometry in one eye per dog at 96 and 97 months after the initiation of galactose feeding. Intraocular pressure (IOP) was measured once in the morning by pneumatonometry. Anterior chamber depth was measured by A-scan. At the end of the experiment, eyes were enucleated and processed for histological examination. Dogs fed galactose diet for 97 months had significantly (p<0.05) increased body weights but similar IOP and anterior chamber depth compared to the other groups, and significantly (p=0.05) reduced aqueous flow compared to the control group (4.4+/-2.2 vs. 6.8+/-2.4 microl/min, mean+/-standard deviation, respectively). Additionally, aqueous flow decreased in the Reversal group to 3.1+/-1.3 microl/min (p=0.002). This decrease correlated with morphological changes of the ciliary processes. Like patients with insulin-dependent diabetes mellitus, galactose-fed dogs demonstrate reduced aqueous flow. This reduction was irreversible and independent of the retinopathy present. This animal model may be useful for the study of aqueous humor dynamics in diabetes.

The Unfolded Protein Response in Lens Epithelial Cells from Galactosemic Rat Lenses

PURPOSE

Diabetic complications are associated with hypoglycemia and hyperglycemia. The purpose of this study was to investigate the effect of both glucose deprivation and hyperglycemia on the induction of endoplasmic reticulum (ER) stress and the subsequent activation of the unfolded protein response (UPR) that results in apoptosis in in vitro cultured lens epithelial cells (LECs) and in vivo cataract formation in galactose-fed rats.

METHODS

Lenses from rats fed a standard diet containing 50% galactose with or without an aldose reductase inhibitor (ARI) were investigated. Transformed human LECs were cultured in standard 10% FCS-DMEM containing various concentrations of sugar. UPR-specific proteins from both the rat lenses and lens cultures were quantified by protein blot analysis. Cell death was evaluated with TUNEL staining and ethidium homodimer-1 (EthD) dyes. Reactive oxygen species (ROS) were quantified with H2-DCF, and free glutathione (GSH) levels were measured with a commercial GSH quantification kit.

RESULTS

Increased apoptosis of the LECs was observed in the lenses of rats fed the galactose diet for 5 to 9 days, and nuclear cataracts subsequently developed in these lenses after 13 to 15 days. Protein blot analysis of the LECs from these galactose-fed rats showed higher levels of the UPR-specific proteins Bip/GRP78, ATF4, and CHOP. These LECs also demonstrated activation of the UPR-specific procaspase-12 and the increased presence of ROS, whereas GSH was reduced. Because these results indicate that the UPR is activated in LECs along with the production of ROS and apoptosis during cataract formation in the galactose-fed rats, subsequent studies were conducted to determine the role of nonenzymatic glycation, osmotic stress, and oxidative stress on these biochemical processes. In vitro cultures of human LECs showed that the UPR was induced by osmotic and oxidative stress, but not by glycation. In addition, the UPR and apoptosis in LECs was induced by glucose deprivation. The ARI blocked the induction of the UPR, cell death, and cataract formation.

CONCLUSIONS

The UPR that is induced by abnormally high or low concentrations of sugar is linked to the production of ROS, increased apoptosis in LECs, and cataract formation. The inhibition of the UPR induction by ARI suggests that osmotic stress may be the primary inducer of the UPR. Modulation of the UPR pathways may offer novel methods for the development of therapeutic tools to delay cataracts.

Nitric oxide synthases modulate progenitor and resident endothelial cell behavior in galactosemia

We used knockout animals of either inducible nitric oxide synthase (iNOS(/)) or endothelial NOS (eNOS(/)) to characterize the role of NOS in galactosemia, a model of diabetic retinopathy. NADH oxidase and nitrotyrosine were used as biomarkers of oxidative stress and vascular dysfunction. These animals were engrafted with hematopoietic stem cells (HSC) expressing green fluorescence protein (gfp(+)) to characterize the contribution of HSC and endothelial progenitor cells to neovascularization. Increased NADH oxidase activity and superoxide generation occurred in all galactose-fed mice. eNOS(/) mice demonstrated increased iNOS immunoreactivity in their retinal vasculature. Nitrotyrosine levels were low at baseline in the wild-type (WT) mice, eNOS(/) and iNOS(/) mice, and the galactose-fed iNOS mice and increased following galactose feeding in eNOS(/) and WT. Galactose-fed WT.gfp and iNOS(/).gfp chimeric animals had areas of perfused new vessels composed of gfp(+) cells. In contrast, galactose-fed eNOS(/).gfp mice produced copious, unbranched, nonperfused tubes. Thus, nitric oxide modulates HSC behavior and vascular phenotype in the retina. Although there is increased NADH oxidase and superoxide in galactosemic mice of all isoforms, iNOS is the source of nitric oxide responsible for peroxynitrite and nitrotyrosine formation that leads to the pathology observed in galactosemic mice.

La galactosémie congénitale : une révélation singulière

Congenital galactosaemia reveals usually in the second and third weeks of life with a severe liver dysfunction. We report on a case of congenital galactosaemia with, on the one hand, an early onset liver failure, without any free interval, and on the other hand, an hemophagocytic syndrome as a severe secondary outbreak with pulmonary haemorrhage. Appropriate diet led to normalisation of liver function. Hemophagocytosis, probably linked to an associated Klebsiella Pneumoniae sepsis, had a favourable outcome after antibiotic and corticosteroid therapy.

[Galactosemia: the genotype and phenotype of seven patients]

INTRODUCTION

Despite early dietary therapy, many patients with galactosemia show a neurodegenerative disease specially evident in speech impairment and movement disorders. Magnetic resonance imaging of the brain, show cerebral white matter changes with hypomielinization bilateral and symetrical periventricular hypersignal in T2.

PATIENTS AND METHODS

We presented clinical and neuroradiological data of seven children (3 to 12 years of age) with classical galactosemia. All had a typical presentation in neonatal period. Two children had normal development (10 and 12 years-old), four presented developmental delay (10, 7, 4 and 3 years-old), and one showed a dystonic cerebral palsy (kernicterus).

RESULTS

The brain MRI showed the typical involvement of white matter, in five children, and basal ganglia abnormalities in the kernicterus patient. Three patients are homozygous for Q188R mutation and two are compound heterozygous.

CONCLUSION

We found a positive correlation among developmental delay, white matter involvement and Q188R mutation.

Inhibitor of apoptosis proteins and ovarian dysfunction in galactosemic rats

Galactosemia is a genetic disease with deficiency of galactose-1-uridyltransferase, resulting in the accumulation of galactose or galactose-1-phosphate in the blood and tissues. Rats were fed with normal rat chow and with a high-galactose diet for 4 weeks to give control and galactosemic groups, and their ovarian function was studied. The two groups of rats were injected with pregnant mare's serum gonadotrophin (PMSG) and were killed at different time points after human chorionic gonadotrophin (hCG) injection. The number of oocytes ovulated in the controls was significantly higher than in the galactosemic group. Morphometric studies of the ovaries also showed a higher number of corpora lutea in the controls. Western blot analysis of granulosa cells showed that the overall expressions of Fas and FasL were lower in the control group and their expressions of inhibitor of apoptosis proteins (IAPs) were higher than in the galactosemic group, especially at 8 h post hCG injection. TDT-mediated dUTP-biotin nick end-labeling (TUNEL) and immunohistochemical staining of ovarian sections with Ki-67 and IAPs showed more apoptotic granulosa cells in the galactosemic group and the expressions of IAPs in granulosa cells also confirmed the result of the Western blot. These findings support our hypothesis that ovarian dysfunction in galactosemic rats is due to increased apoptosis in granulosa cells of maturing follicles.

Peripheral nerve regeneration in galactosaemic rats

The use of galactosaemia as a model for some aspects of diabetic polyneuropathy allows the influence of glycation to be studied independently of other effects. There are well-studied abnormalities of the peripheral nerves in galactosaemic rats, one of which is that the efficiency of regeneration is initially reduced. One possible cause could be that glycated myelin debris in macrophages is less degradable and interferes with macrophage function. Macrophage recognition and ingestion of myelin glycosylated in vitro increases with the duration of incubation in a sugar-rich medium. This study was performed to investigate a possible correlation between galactosaemia and regeneration, together with the role of macrophages. Galactosaemia was induced by adding galactose to the rats' diet for 2 months before injury. Following a crush lesion to the sciatic nerve, regeneration was found to be delayed, demonstrated by a reduction in mean myelinated fibre size and density 1 month after crush, although, 2 and 3 months later, the differences did not reach statistical significance. There were also more macrophages in the galactosaemic rats than in the control animals at all time points. The initial delay in regeneration in galactosaemic rats was therefore only temporary and there was little evidence of long-term deleterious effects. In addition to the morphometric results, immunohistochemistry showed that there were more macrophages in the galactosaemic rats than in the control animals at all time points. Correlating macrophage and myelinated fibre counts suggests that the persistence of debris-containing macrophages does not appear to have a significant inhibitory effect on nerve regeneration. No evidence was found for persistent basal laminal tubes around the regenerating clusters.

Pyruvate modulates antioxidant status of cultured human lens epithelial cells under hypergalactosemic conditions

Lens epithelial cells are the metabolic unit of the lens and antioxidant enzymes are mainly concentrated here. The purpose of this study was to maintain human lens epithelial cells (HLEC) in culture and examine the status of antioxidant enzymes (glutathione peroxidase (GSHPx), catalase (CAT), glutathione-S-transferase (GST)), lipid peroxidation product malondialdehyde (MDA) and glutathione (GSH) levels in these cells under normal as well as hypergalactosemic (30 mM galactose) conditions. Further, effect of pyruvate, a physiological antioxidant has also been evaluated on these parameters. For conducting experiments, anterior capsule specimens obtained from fresh cadaver eyes from eye bank were cultured in Dulbecco's Modified Eagle's Medium (DMEM) supplemented with 20% fetal calf serum. Upon confluency, the cells were subcultured in three separate flasks containing DMEM alone (normal group), DMEM + 30 mM D-galactose (control group), DMEM + 30 mM D-galactose + 5 mM pyruvate (test group) and incubated for 24 or 72 h. These cells were observed under the phase contrast microscope for any morphological changes and harvested for the estimation of various antioxidant parameters. Our results show significant weakened antioxidant defense in HLEC when incubated in the presence of galactose as compared to normal. Addition of pyruvate significantly modulated levels of GSH, MDA, GSHPx, CAT and GST.

Effect of galactose diet removal on the progression of retinal vessel changes in galactose-fed dogs

PURPOSE

Feeding dogs a diet containing 30% galactose induces experimental galactosemia and results in the formation of diabetes-like microvascular lesions of the retina. The appearance and progression of these retinal lesions can be arrested in a dose-dependent manner by treating these dogs with aldose reductase inhibitors from the onset of galactosemia. To determine whether the elimination of galactosemia can also reduce the progression of retinal lesions, the galactose diet was removed from the galactosemic dogs after either the appearance of pericyte ghosts or formation of microaneurysms.

METHODS

Ten control dogs were fed a normal diet, and 50 dogs were fed a diet containing 30% galactose. The galactose diet was removed from 15 dogs after 24 months, the time at which pericyte ghosts had previously been observed to develop, and from another 15 dogs after 31 months, when microaneurysms had previously been observed to develop. Eighteen dogs were continued on a galactose diet. Beginning at 24 months, eyes from each group were enucleated at approximately 6-month intervals. Changes in retinal lesions were quantified by computer image analyses.

RESULTS

Significant (P < 0.05-0.01) increases in the endothelium-pericyte (E-P) ratio and decreases in pericyte density were observed with increased duration of galactose feeding. Although no reversal of retinal lesions occurred, differences in the progression of retinal lesions between the galactose-fed and galactose-deprived groups became evident after 12 to 24 months.

CONCLUSIONS

Discontinuation of galactose in the diet at the initial stages of background retinopathy beneficially delays the progression of retinal lesions.

Pyruvate inhibits galactosemic changes in cultured cat lens epithelial cells

An attempt was made to maintain cat lens epithelial cells (CLEC) in culture and study the morphology, growth and survival of these cells in vitro. The influence of incorporation of galactose (30 mM) into the culture medium on the morphology and biochemistry of CLEC in the primary culture was then investigated. To establish the effect of galactose on CLEC, various biochemical parameters associated with galactosemic cataract such as aldose reductase (AR), Na+K+ATPase, glutathione, polyol and soluble/insoluble proteins were estimated after 24 h of incubation. The effect of pyruvate (5 mM), a 'physiological antioxidant', on the changes induced by galactose in CLEC was studied. CLEC in culture showed regular hexagonal cells with prominent nuclei. The CLEC culture attained confluency in 11 days during primary culture and semiconfluency in 14 days in two subsequent passages. Vacuolization and significantly raised AR activity, polyol levels and insoluble protein contents were observed; they had no effect on Na+K+ATPase and soluble protein after 24 h of incubation in the culture medium with galactose. Supplementation of pyruvate (5 mM) resulted in a lesser number of vacuoles together with a positive modulation of these parameters.

Inhibitory effect of lycopene on cataract development in galactosemic rats

This study investigated the effect of antioxidants on cataract formation in galactosemic rats. Two antioxicants were compared: lycopene, a carotenoid derived from tomato, and butylated hydroxytoluene (BHT), a known antioxidant substance. The control group was fed with galactose 30%. The experimental groups received, in addition to galactose 30%, either lycopene 0.8% or BHT 0.2%. Cataractogenesis was evaluated by the incidence of cataract, grading of cataract, histology of the lenses, aldose reductase (AR) activity, protein levels, and reduced glutathione (GSH) contents in the lens. In both experiemtal groups: 1) the incidence and grading of cataract were lower, 2) the protein levels and GSH content were higher, and 3) the AR was decreased compared to the control group. In conclusion, "natural antioxidants" such as lycopene derived from tomato have a similar effect as BHT in delaying cataractogenesis in rats.

Functional and structural studies of alpha-crystallin from galactosemic rat lenses

Chaperone-like activity and structural changes of lens alpha-crystallin from rats fed with galactose at various time intervals have been studied using high-performance liquid chromatograph (HPLC), circular dichroism (CD), and 1-anilinonaphthalene-8-sulfonic acid (ANS) fluorescence emission. It was found that chaperone-like activity of alpha-crystallin from galactose-fed rats toward dithiothreitol (DTT)-induced insulin B aggregation started to decrease after 3 weeks and decreased significantly after 5 weeks. Consistent results were observed in lens morphology, and lens opacity slightly developed after 3 weeks and became obvious after 5 weeks. HPLC analysis for chaperone function showed that the formation of high molecular weight aggregates (HMWA) of alpha-/gamma-crystallins decreases with the increase of galactose-feeding time, revealing that chaperone-like activity is concomitant with the formation of HMWA. Circular dichroism results showed the reduction of beta-sheet structure and loss of microenvironment of aromatic-type amino acids for opaque lenses, indicating alpha-crystallin's secondary and tertiary structure changed with the development of the lens opacity. ANS binding site estimated by Klotz equation showed it is 1.5 times higher at room temperature and is 2.4 times higher at 58 degrees C for age-matched normal alpha-crystallin than for 5-week galactose-fed lens alpha-crystallin, indicating opaque lens alpha-crystallin loses the ability to assemble into an appropriately placed hydrophobic regions. The overall results accordingly indicated that galactose-induced cataractous alpha-crystallin has disordered structure, leading to the loss of its chaperone-like activity.

Molecular basis for phenotypic heterogeneity in galactosaemia: prediction of clinical phenotype from genotype in Japanese patients

We identified 14 mutations in 15 Japanese subjects from 13 families with galactose-1-phosphate uridyltransferase (GALT) deficiency using denaturing gradient gel electrophoresis (DGGE) and direct sequence analysis. These mutations accounted for 22 (96%) of 23 mutant alleles in 15 Japanese subjects. The mutational spectrum included nine missense mutations (M142V, G179D, A199T, R231H, W249R, N314D, P325L, R333Q, and R333W), two deletions (L275fsdelT and Q317fsdelC), a nonsense mutation (W249X), and two splicing mutations (V85-N97fsdel38bp and IVS4nt+1). Ten of the 14 mutations have not been reported in Caucasians. Differences in frequency and spectrum of GALT mutations suggest that the mutations may have occurred after racial divergence of Caucasians and Asians. The Duarte variant in Japanese was associated with the N314D mutation, g.1105G > C, g.1323G > A, and g.1391G > A (SacI -) polymorphisms, as in Caucasians. The Duarte variant may have occurred before racial divergence, and was an ancient mutation. In vitro GALT activities of nine missense mutations were determined by a COS cell expression system, and indicated between 1.3% and 35% of wild-type control. Patients with R333Q (29% in vitro GALT activity) or A199T (35%) showed mild clinical phenotypes, i.e. no ovarian failure or neurological deterioration. Genotype determination is useful for predicting biochemical and clinical phenotypes in classic galactosaemia, and can be of further help in managing patients with this disorder.

Cataract development in 12-month-old rats fed a 25% galactose diet and its relation to osmotic stress and oxidative damage

We attempted to clarify the pattern of cataract development in 12-month-old rats fed a 25% galactose diet and to assess the relation of cataract development with osmotic stress and oxidative damage. In lenses of 12-month-old male Wistar rats fed a 25% galactose diet over an 8-month period, suture accentuation appeared at 6 months of galactose feeding and then opacities developed from the anterior subcapsular cortex toward the posterior subcapsular cortex, reaching the nuclear region at 8 months of galactose feeding. Increases in lens galactitol and lipid peroxide contents and a decrease in lens reduced glutathione content occurred at 4, 6 and 8 months of galactose feeding. The increase in lens lipid peroxide content and the decrease in lens reduced glutathione content were accelerated with an increase in feeding period, while the increase in lens galactitol content was decelerated. An increase in lens water content and a decrease in lens protein content occurred at 6 and 8 months of galactose feeding. The lens vitamin E content increased at 6 months of galactose feeding and this increase was concomitant with increases in serum vitamin E and total cholesterol concentrations. The serum lipid peroxide concentration increased at 4 and 6 months of galactose feeding. The present results indicate that in lenses of 12-month-old rats fed a 25% galactose diet, suture accentuation appears initially and then opacities develop from the anterior subcapsular cortex toward the posterior subcapsular cortex, finally reaching the nuclear region. These results also suggest that in the galactosemic aged rats, osmotic stress would mainly contribute to cataract formation, while oxidative damage could be linked to both cataract formation and progression, although an increase in lens vitamin E content occurs during the cataract development.

Peripheral nerve structure and function in long-term galactosemic dogs: morphometric and electron microscopic analyses

Experimental galactosemia for activating the polyol pathway is used extensively to explore the pathogenesis of diabetic complications. However, despite the presence of severe neuropathy in galactosemic rats, changes in the peripheral nerve have not been well established in galactosemic dogs. We therefore conducted biochemical, electrophysiological, and morphometric studies on peripheral nervous systems (PNS) in dogs given a 30% galactose diet for 44 months. Age- and sex-matched dogs given a 30% cellulose diet were used as control. Chronic galactosemia resulted in accumulation of galactitol and decrease in myo-inositol in the sciatic nerve. Electrophysiological and teased fiber analyses demonstrated no significant abnormalities in the ulnar and peroneal nerves in galactosemic dogs. Morphometric analyses revealed a tendency of myelinated fiber atrophy (24% reduction of average fiber size) associated with 20% decrease (P < 0.05 vs control) in mean myelinated fiber occupancy rate in the peroneal nerve in galactosemic dogs. In the anterior mesenteric ganglion, there was a slight but significant increase (8%) in mean neuronal cell size in galactosemic dogs (P < 0.05 vs control). Electron microscopy revealed that galactosemia did not produce dystrophic and degenerative changes in the autonomic ganglion in dogs. We conclude that structural and functional changes in the PNS of galactosemic dogs are mild and different from those of the rat model. These findings suggest that the severity of peripheral neuropathy induced by chronic galactosemia may be species dependent.

Localization of protein kinase C in normal and galactosemic bovine lens epithelial cells in culture

The localization of the two major isoforms of protein kinase C (PKC), PKCalpha and PKCgamma, present in normal and galactosemic bovine lens epithelial cells in culture, was determined using PKC isoform-specific antisera and visualized with FITC-conjugated secondary antisera. The results indicated that the localization of PKC changed upon exposure to 40 mM galactose after 1 day. The subcellular distribution of control cells was cytoplasmic and perinuclear for PKCalpha, while, in 40 mM galactose-treated cells, PKCalpha was also localized to nuclei. In contrast, upon exposure to 40 mM galactose the PKCgamma of the lens epithelial cells was observed in nucleoli. These results suggest that the subcellular distribution of the PKC isoforms in bovine lens epithelial cells differs and is altered upon exposure to 40 mM galactose.

An aldose reductase inhibitor and aminoguanidine prevent vascular endothelial growth factor expression in rats with long-term galactosemia

OBJECTIVE

To study the effects of an aldose reductase inhibitor (ARI-509, Wyeth-Ayerst, Princeton, NJ) and aminoguanidine (AMG), agents that have been reported to prevent or delay diabetic retinopathy, on retinal vascular abnormalities and the immunocytochemical expression in the retina of vascular endothelial growth factor (VEGF) in rats maintained for up to 2 years on a 50% galactose diet.

METHODS

Albino rats were placed on a control diet, a diet containing 50% galactose, or the 50% galactose diet containing either ARI-509 or AMG. Treatment with ARI-509 or AMG was initiated at the beginning of the experiment or after 12 months of galactose feeding. After 22 to 24 months, the rats were killed and the retinal vasculature from half of one eye was isolated by trypsin-elastase digestion for semiquantitative evaluation of retinal vascular lesions. The other half of the retina was prepared for immunocytochemistry and stained for the presence of VEGF, factor VIII, vimentin, and glial fibrillary acidic protein. Red blood cells, sciatic nerves, and a portion of the retina from the second eye were assayed for glucose, galactose, fructose, sorbitol, galactitol, and myo-inositol. Red blood cells were also assayed for galactosylated hemoglobin.

RESULTS

Galactose-fed animals developed a vascular retinopathy characterized by severe cellular loss in the retinal capillaries and intensification of periodic acid-Schiff staining of the vascular basement membranes. Some animals also displayed dilation and hypercellularity of vessels in the posterior retina. These changes were substantially reduced in animals receiving ARI-509 from the beginning of the galactose diet, but were unaffected in all of the other treatment groups. None of the rats receiving ARI-509 or AMG treatment, whether initiated from the onset or after 12 months of galactosemia, demonstrated VEGF immunoreactivity. With the exception of the animals receiving ARI-509 from the beginning of the experiment, all of the galactose-fed animals developed dense cataracts within 6 weeks of the beginning of the galactose diet. Galactitol levels in animals receiving ARI-509 were 86% to 93% lower in red blood cells, retina, and sciatic nerve than those in the other galactose-fed groups.

CONCLUSIONS

Although ARI-509 and AMG have different abilities to delay or prevent the diabetic-like retinopathy in galactosemic rats, even when substantial retinal microvascular acellularity occurs, both drugs prevent the immunocytochemical expression of VEGF. These results suggest that factors other than hypoxia may be responsible for VEGF expression in the retina, and that aldose reductase inhibitors and AMG have potential roles in preventing such expression and, thus, perhaps preventing retinal neovascularization.

Quantitation of galactosemic cataracts in dogs using magnetization transfer contrast-enhanced magnetic resonance imaging

PURPOSE

Magnetic resonance imaging (MRI) is becoming increasingly important for the diagnosis and characterization of ocular pathologies. A drawback to this technique is that image contrast between different regions of tissue can be obscured because of the similarity of their nuclear magnetic resonance relaxation parameters. This problem is addressed by magnetization transfer contrast (MTC) enhancement, a MRI technique that generates high-contrast images based on characteristic tissue differences resulting from the interaction of water and macromolecules. The purpose of this study was to investigate the feasibility of using MTC-enhanced imaging to monitor quantitatively the lens changes associated with sugar cataract formation in galactose-fed dogs.

METHODS

Male beagles fed a diet containing 30% galactose were periodically examined by MRI for changes in tissue character. Each examination included a gradient recalled echo image (M0), an MTC-enhanced gradient recalled echo image (Ms), a T1 image determined from a one-shot T1 imaging sequence, and a T1-weighted image taken from the raw T1 data. Average values were obtained for several regions of interest and tabulated. These were correlated with cataractous stages visually observed by slit lamp biomicroscopy and retroillumination photography.

RESULTS

Enhanced image details of the lens and anterior segment that documented osmotic changes from initial cortical vacuole formation to cortical and nuclear changes associated with advanced sugar cataracts were characterized from measurements of parameters obtained from M0, Ms, T1-weighted, and T1 images. Changes in the cross-sectional areas of lenses during sugar cataract formation also were documented. The magnetic resonance images showed visible changes from the onset of cortical vacuole formation. Region of interest (ROI) analysis of the images showed tissue changes occurring throughout the cataract progression.

CONCLUSIONS

The MTC-enhanced MRI technique is well suited to detecting lens changes associated with cataractogenesis. All but the earliest changes were readily apparent from the images with no further analysis. Graphic ROI analysis was able to detect regional changes associated the cataract progression for all degrees of severity. Furthermore, the images demonstrated changes in size and shape that would not be detectable by visual inspection.

A mouse model of diabetic retinopathy

OBJECTIVE

To obtain a model of diabetic retinopathy to which modern methods of genetic engineering may be applied, by determining the response of 2 strains of mice to long-term galactose feeding.

METHODS

Both C57BL/6 mice BALB/c mice were fed each of 2 galactose-rich diets (30% and 50% galactose), and trypsin digests of their retinas were compared with those of controls at durations of up to 26 months.

RESULTS

The mortality rate in galactose-fed animals was lower in C57BL/6 mice than in BALB/c mice, and both strains tolerated the 30% galactose diet significantly better than the 50% galactose diet. In C57BL/6 mice fed 30% galactose for 21 to 26 months, saccular microaneurysms were observed in the retina, together with significant increases in the thickness of capillary basement membrane and the prevalence of acellular capillaries and pericyte ghosts. The 50% galactose diet caused significantly more acellular capillaries than normal by 15 months, but excessive mortality precluded study at longer durations. The frequency of acellular capillaries also was greater than normal in BALB/c mice fed 30% galactose for 21 months. Retinal polyol levels in galactose-fed mice were found to be lower than those in galactosemic rats.

CONCLUSION

The mouse may provide an inexpensive model suitable for in vivo study of the pathogenesis of diabetic retinopathy using molecular biological techniques.

Liquefaction of cortical tissue in diabetic and galactosemic rat lenses defined by confocal laser scanning microscopy

PURPOSE

To investigate whether a histologic link exists between osmotic fiber cell swelling and cortical tissue liquefaction in experimentally induced diabetic and galactosemic cataractogenesis of the rat lens.

METHODS

Confocal laser scanning microscopy, in conjunction with specific membrane labels and correlative transmission electron microscopy, was used to image large cortical areas with precise definition of the individual cells.

RESULTS

In both cataract models, tissue liquefaction--defined as the disintegration of tissue and the appearance of large fluid-filled spaces--typically was limited to a discrete zone in the lens cortex. The borders of the liquefaction zone were characterized by transitions between normal-appearing cells and swollen cells, which gained in size as plasma membranes ruptured and cytoplasmic contents fused and ultimately burst, thereby contributing to the formation of large fluid-filled spaces. During cataractogenesis, before tissue liquefaction became evident, selected fiber cells appeared swollen and accumulated specifically in the zone destined for tissue liquefaction. With increasing duration of diabetes or galactosemia, swollen fiber cells in this zone became more frequent and enlarged, resulting first in tissue disorder and then in tissue disintegration and the formation of large fluid-filled spaces.

CONCLUSIONS

New imaging protocols strongly support a direct involvement of lens fiber cell swelling in the liquefaction of cortical tissue. The appearance of swollen fiber cells in the lens cortex, therefore, can be used as an early indicator of the histopathology of sugar cataractogenesis.

Capillary lesions develop in retina rather than cerebral cortex in diabetes and experimental galactosemia

OBJECTIVE

To isolate microvessels from cerebral cortex of dogs with alloxan-induced diabetes and dogs with experimental galactosemia to compare the prevalence of microvascular lesions in cerebral cortex with that in retina.

METHODS

Microvessels were isolated from cerebral cortex of experimental animals using a sieving method, and compared with the retinal vasculature isolated from the same animals using the trypsin digestion method.

RESULTS

Dogs with diabetes or experimental galactosemia of 5 years' duration had retinopathy that was morphologically indistinguishable from that of humans with diabetes, including microaneurysms, acellular capillaries, and pericyte ghosts. These lesions never were seen in cerebral cortical vessels of the same animals. The only morphologic abnormality observed in cerebral capillaries of dogs with diabetes and dogs fed galactose was thickening of basement membrane.

CONCLUSIONS

Local influences in the eye apparently play an important role in the development of diabetic retinopathy. Current hypotheses about the pathogenesis of the retinopathy do not account adequately for such differences in the tissue distribution of vascular lesions.

Magnetic resonance imaging of the galactosemic dog eye using magnetization transfer contrast

Magnetization transfer contrast (MTC) enhanced magnetic resonance (MR) imaging is a technique that generates high contrast images based on characteristic tissue differences resulting from the interaction of water and macromolecules. In this study, the feasibility of applying this technique to documenting the progression of osmotic sugar cataract formation was investigated in male beagles, initially 6 or 24 month old, fed a diet containing 30% galactose. MTC enhanced magnetic resonance imaging was periodically conducted on these animal's eyes at 2-Tesla. The lens MR images were compared to photographs obtained by photo-slit lamp and retroillumination photography. The MTC technique provided improved image details of the lens and anterior segment that documented osmotic changes from initial cortical vacuole formation to cortical and nuclear changes associated with advanced sugar cataracts. The latter could not be observed by photo-slit lamp or retroillumination photography.

Endothelial changes in galactose-fed dogs

Specular microscopic studies indicate that the size (polymegathism) and shape (pleomorphism) of the hexagonal corneal endothelial cells change in diabetics. Similar morphometric changes of the corneal endothelium have also been experimentally observed in diabetic rats as well as in diabetic and galactose-fed dogs and concomitant administration of aldose reductase inhibitors reduced these morphological changes. The purpose of this study was to examine whether corneal endothelial changes in galactose-fed dogs are reversible by the marked reduction of galactitol production after stopping prolonged galactose feeding. Ten control dogs were fed a normal diet, while 48 dogs were fed a diet containing 30% galactose. The galactose diet was removed from 15 dogs after 24 months at which time pericyte ghosts in the retina had developed and another 15 dogs were removed from the galactose diet after 31 months when retinal microaneurysms had developed. Eighteen dogs remained on galactose diet throughout the study (38 months). Specular microscopy was conducted on members of all groups after 38 months of study and the photographs were analyzed in masked fashion on the Bambi image analysis system. The evaluation of the corneal endothelial cells revealed significant differences in the cell size and density between galactose-fed dogs in the three groups and normal, age-matched control dogs. Corneal endothelial changes were not significantly reduced in dogs fed galactose for either 24 months or 31 months and then fed a normal diet for 14 and 7 months, respectively, indicating that amelioration of endothelial cell changes requires therapy prior to the advent of endothelial morphologic changes.