Plasma insulin content and glucose tolerance in homocystinuria

Leptin concentrations and SCD-1 indices in classical homocystinuria: Evidence for the role of sulfur amino acids in the regulation of lipid metabolism

BACKGROUND

We describe body composition, lipid metabolism and Stearoyl-CoA desaturase-1 (SCD-1) indices in patients with classical homocystinuria (HCU).

METHODS

Eleven treated HCU patients and 16 healthy controls were included. Body composition and bone mineral density were assessed by dual X-ray absorptiometry. Sulfur amino acids (SAA) and their derivatives (total homocysteine, cysteine, methionine, S-adenosylmethionine, S-adenosylhomocysteine, and glutathione), lipids (free fatty acids, acylcarnitines, triglycerides and lipoproteins), glucose, insulin, leptin, adiponectin, and isoprostanes were measured in plasma. Insulin resistance was evaluated by HOMA-IR. To estimate liver SCD-1 activity, SCD-16 [16:1(n-7)/16:0] and SCD-18 [18:1(n-9)/18:0] desaturation indices were determined.

RESULTS

In HCU patients, SCD-16 index was significantly reduced (p=0.03). A trend of an association of SCD-16 index with cysteine was observed (r=0.624, p=0.054). HCU patients displayed lower lean mass (p<0.05), with no differences in fat mass percentage. Leptin and low-density lipoprotein concentrations were lower in HCU patients (p<0.05). Femur bone mineral density Z-scores were correlated with plasma cysteine (r=0.829; p=0.04) and total homocysteine (r=-0.829; p=0.04) in HCU patients.

CONCLUSIONS

We report alterations in leptin and SCD-1 in HCU patients. These results agree with previous findings from epidemiologic and animal studies, and support a role for SAA on lipid homeostasis.

Anesthetic implications of the child with homocystinuria

We present a 7 1/2-year-old girl with type I homocystinuria who required anesthetic care during repair of bilateral ectopia lentis. Homocystinuria is an autosomal recessive disorder and represents the second most common error of amino acid metabolism. Defective function of the enzyme cystathionine synthetase results in elevated serum levels of methionine and homocysteine. Physiologic disturbances include an increased risk of thromboembolic events and hypoglycemia. Perioperative measures to prevent thromboembolic events include diet therapy to lower serum methionine and homocysteine levels, adequate preoperative hydration, maintenance of intraoperative cardiac output, and the use of pneumatic stockings to prevent peripheral stagnation of blood. Hypoglycemia is thought to be due to alterations in insulin release associated with high levels of circulating sulfur-containing amino acids such as methionine. Perioperative measures include normalization of serum methionine and administration of exogenous glucose during periods of fasting.

Ectopia lentis

Ectopia lentis was first described more than 200 years ago, but its value as a significant diagnostic clue to the presence of other ocular and systemic disorders has only recently been appreciated. Ectopia lentis may cause a marked reduction in visual acuity, which varies with the type and degree of dislocation and the presence of other ocular abnormalities. An approach to the diagnostic evaluation of the patient with ectopia lentis is outlined. The differential diagnosis is reviewed in detail both clinically and histologically. The complications of ectopia lentis and the appropriate management of affected patients are discussed.

Blood glutathione in various phases of insulin-dependent diabetes mellitus in children

Reduced glutathione (GSH) in whole blood was studied in 15 insulin-dependent juvenile diabetic patients at onset of diabetes (group A). In 5 of these patients the blood GSH concentration was followed during the first month after onset. The blood GSH content was also analyzed in 16 children with insulin-dependent diabetes mellitus (IDDM) with a duration of diabetes of more than 2 years (group B), and in a control group of 76 healthy children (group C). The GSH levels in groups A, B and C were 48.3 +/- 5.7, 47.1 +/- 4.6 and 47.6 +/- 4.3 mg/100 ml erythrocytes, respectively. Thus, there were no significant differences between the patients and the control group. In group A, there were no significant differences in blood GSH values at onset and 1 month later.

Homocysteine theory of arteriosclerosis

Arteriosclerotic plaques were found in the aorta and arteries of rabbits given homocysteine thiolactone, methionine or homocysteic acid, both parenterally and in a synthetic diet. Animals given large doses of parenteral methionine or homocysteine thiolactone died of pulmonary embolism and pulmonary infarct. Pyridoxine prevented thrombosis and pulmonary embolism but did not prevent arteriosclerotic plaques. These findings and previous work, showing a new matabolic pathway for sulfate ester synthesis from methionine, the somatotrophic activity of homocysteic acid, and control of cellular growth and intercellular matrix synthesis by homocysteine derivatives, suggest a theory to explain aspects of the pathogenesis of arteriosclerosis.