Aldose reductase inhibitors and galactose toxicity in neonatal and maternal rat lenses

Esculetin and idebenone ameliorate galactose-induced cataract in a rat model

Cataract is the principal cause of blindness. The enzyme, aldose reductase (AR) is a key player in polyol pathway. Buildup of polyols and oxidative stress are the main causes of cataractogenesis. This study investigated the cytoprotective properties of esculetin and idebenone in galactose-induced cataract. Rats were partitioned into four groups each of ten rats. Control group was fed with normal diet; group 2 rats were fed with galactose diet (50%); groups 3, 4 rats were fed with galactose diet concurrently with either esculetin (50 mg/kg BW) or idebenone (100 mg/kg BW), for 20 days. The study revealed that esculetin and idebenone significantly reduced the elevated levels of Bax/Bcl-2 ratio, malondialdehyde, and DNA fragmentation and increased total antioxidant capacity level in lenses compared to the cataract-induced group. Only esculetin decreased AR, galactitol, and advanced glycated end products levels in lenses. Histopathological examinations supported the biochemical findings. Esculetin and idebenone may have chemopreventive effects for sugar cataract. PRACTICAL APPLICATIONS: Cataract is an age-related disease that might cause blindness in older adult people. Presently, no absolute pharmacological treatment is accessible for cataract. The use of natural products or their derivatives attract particular attention in modern medicines as they are believed to be safer with few or no side effects. Esculetin is a polyphenolic compound found in many medicinal plants. Idebenone is a synthetic analogue of coenzyme Q10. The current study is an approach to explore the anticataract effects of esculetin and idebenone in galactose-induced cataract in rats. Our study proved that both agents have anticataractogenic potentials due to their antioxidant and antiapoptotic properties.

Urine and plasma galactitol in patients with galactose-1-phosphate uridyltransferase deficiency galactosemia

Urinary excretion of galactitol was determined in 95 normals (N/N), 67 galactosemic (G/G), and 39 compound heterozygotes for the Duarte and galactosemia genotype (D/G). Galactitol excretion is age-dependent in both normal individuals and patients with classic galactosemia on lactose-restricted diets. In galactosemic patients who are homozygous for the Q188R mutation, urinary galactitol levels were fivefold to 10-fold higher than those of normal subjects of comparable age. All but a few patients with classic galactosemia with the Q188R mutation and another mutant G allele had urinary excretion comparable to the Q188R homozygous patients. African-American galactosemic patients with the S135L mutation of the galactose-1-phosphate uridyltransferase (GALT) gene also excreted abnormal quantities of galactitol. Most subjects with a Duarte allele and a G allele excrete normal amounts of the sugar alcohol. There is a correlation between galactitol excretion and red blood cell (RBC) galactose-1-phosphate (gal-1-P). Plasma galactitol was also elevated in galactosemic patients (3.4 to 23.2 micromol/L; undetectable in normal individuals). In contrast to the decrease in urinary galactitol with age, plasma levels remain in a narrow concentration range with no significant difference with age. Urine and plasma galactitol distinguish galactosemic patients from normals. In addition, urinary galactitol excretion may be an important parameter for the assessment of steady-state galactose metabolism in galactosemia.

The role of polyols in the pathophysiology of hypergalactosemia

Cellular accumulation of galactitol has been suggested to cause the apparent dietary-independent, long-term complications in classic galactosemia. Experimental animals rendered hypergalactosemic by galactose feeding accumulate tissue galactitol, as well as millimolar quantities of galactose, and manifest biochemical, physiological and pathological abnormalities which are generally eliminated or curtailed by the concomitant administration of an aldose reductase inhibitor. This includes reduced cellular content of the cyclic polyol, myo-inositol, which like galactitol may function as an alternate intracellular osmolyte. However, the abnormalities detected in experimental galactosemic animals are more compatible with findings in experimental diabetes mellitus than in human galactosemia. Because patients with galactokinase deficiency fail to manifest the CNS and ovarian complications which characterize classic galactosemia, yet during long-term lactose restriction excrete comparable urinary quantities of galactitol, this polyol alone is not likely to play an important role during postnatal life in the pathogenesis of long-term complications. Notwithstanding, a role for either galactitol or myo-inositol in an intrauterine toxicity cannot be dismissed.