Glucose metabolism by human cataracts in culture

Diabetes, glaucoma, sex, and cataract: analysis of combined data from two case control studies

Data from two case control studies in Oxfordshire were combined and analysed. The combined study covered 1940 subjects, 723 cases, and 1217 controls, between the ages of 50 and 79 with a response rate of 97% for cases and 94% for controls. Diabetes was shown to be a powerful and highly significant risk factor for cataract with a relative risk of 5.04. More than 11% of cataracts in Oxfordshire are attributable to diabetes. The relative risk did not increase significantly with age within the range 50 to 79 years but was higher in females than in males. For females with diabetes the relative risk was 7.85 with 95% confidence interval from 4.30 to 14.3 compared with 3.42 with confidence interval from 2.05 to 5.71 for males with diabetes. Diabetes remained a powerful risk factor when other identified risk factors had been controlled for. No known mechanism for the development of diabetic complications provides an explanation for the excess risk in females. Combination of the two studies led to better estimates of the relative risk of glaucoma as a risk factor for cataract (3.96 with 95% confidence interval from 2.35 to 6.68). The relative risk appeared to be greater in women than in men but this difference was not statistically significant. There was no significant change in risk with age. Glaucoma is a powerful and independent risk factor for cataract in both sexes and may be responsible for 5% of all cataracts in our area.

Morphological studies of an ion-dependent perinuclear cataract model

The perinuclear region of the rabbit lens is susceptible to alterations in the ionic composition of incubation medium. Rabbit lenses and a comparable cell type, red blood cells, were stressed during ex vivo incubations in isotonic modified Earle's medium with 131 mM NaCl replaced by either 232 mM sucrose or 131 mM choline chloride at pH 7.2 (normal) or 9.2. Our parallel NMR study revealed that these experimental media maintain normal intracellular pH and phosphorus metabolite levels. The present study demonstrates that lens transparency, normal fiber cell ultrastructure and volume were maintained in either sodium chloride or choline chloride containing media at normal or elevated pH. Similarly, normal morphology, mean cell volume (MCV) and mean cell hemoglobin concentration (MCHC), 86.8 +/- 0.03 micron 3 and 33.2 +/- 1.0 g dl-1, respectively, were maintained in red blood cells in either sodium chloride or choline chloride containing media. In sodium chloride deficient media at both normal and elevated pH the lens developed a nuclear cataract based on slit-lamp examination; however, SEM examination showed that fiber cell morphological abnormalities were confined to a narrow band, 50 micron wide, in the perinuclear region of the transition zone. Damage consisted of ruptured cell membranes and an absence of identifiable interdigitations with the combination of sodium chloride deficiency and elevated pH. The major abnormality produced during incubation in sodium chloride deficient medium at normal pH was the presence of numerous smooth-surfaced cellular protrusions along the vertices of the perinuclear fiber cells. In addition, the sodium chloride deficient medium, pH 9.2, produced a volume loss both in the lens and RBC (4.5 +/- 1.5% and 5.6 +/- 1.1%, respectively). The sodium chloride deficient medium, pH 7.4, produced no volume loss in the lens or red blood cells (MCV 86.0 +/- 0.05 micron 3). Further studies indicated that the cataract induced by sodium chloride deficiency (pH 9.2) is irreversible. The mechanism for perinuclear opacification due to ion deficiency remains to be elucidated.

Phosphorus and proton magnetic resonance spectroscopic studies on the relationship between transparency and glucose metabolism in the rabbit lens

We report the results of a series of nuclear magnetic resonance (NMR) experiments designed to investigate the relationship between particular aspects of glucose metabolism and cataract formation in the rabbit lens. The glucose metabolism of the rabbit lens incubated in TC-199 medium containing 5.5 mM glucose, in glucose-deficient medium, and in modified Earle's medium containing 5.5 mM glucose devoid of NaCl, is examined in conjunction with the assessment of lens transparency. Significant age-dependent differences in the phosphorus metabolite profile and in hexosemonophosphate shunt flux, as measured by NMR, were observed in lenses incubated in TC-199 medium containing 5.5 mM glucose. Incubation in glucose-deficient medium for 8 hr results in significant increases in the levels of inorganic phosphate and phosphomonoesters, and decreases in ATP and L-alpha-glycerolphosphate. These levels regain near-normal values after 24 hr incubation in control medium containing 5.5 mM glucose. By contrast, shunt flux is three times the basal level during the recovery period. Lens clarity, as assessed by slit lamp micrography, was maintained throughout the duration of the experiment. Incubation of adult and juvenile lenses for 18 hr in Earle's medium (pH 7.4 or 9.2) containing 5.5 mM glucose, and no NaCl, results in uniform lenticular opacification within 18 hr and changes in ultrastructure of the epithelial and cortical lens fiber cells. No statistically significant change in the NMR visible phosphorus metabolite profile or intralenticular pH is observed for the adult rabbit lens relative to a lens incubated under control conditions. For the juvenile rabbit lens, small, but statistically significant differences in the levels of dinucleotide and uridinediphosphoglucose were observed. Shunt flux, in contrast, is increased two-fold. These results demonstrate that the NMR visible phosphorus metabolite profile of the lens does not necessarily correlate with transparency, and that hexosemonophosphate shunt activity provides a sensitive measure of prior or current lenticular stress.