Monounsaturated and marine omega-3 fatty acids in NIDDM patients

Glucose oversupply increases Delta9-desaturase expression and its metabolites in rat skeletal muscle

AIM/HYPOTHESIS

Previous studies have shown that prolonged glucose infusion causes insulin resistance and triglyceride accumulation in rat skeletal muscle. In this study, we investigated a possible relationship between insulin resistance and the composition of different accumulated lipid fractions in rat skeletal muscle.

METHODS

Continuous glucose infusion was carried out in rats for 7 days. Lipids were extracted from skeletal muscle, separated by thin layer chromatography and fatty acid composition of phospholipids, triglycerides, diglycerides, free fatty acids and cholesterol esters fractions was analysed by gas chromatography. Delta9-Desaturase mRNA was measured by real time polymerase chain reaction. The enzyme activity was measured in the microsomal fractions.

RESULTS

Prolonged glucose infusion (5 days) increased the relative content of palmitoleic acid (16:1 N7) several-fold (2.3- to 5.8-fold) in four out of five lipid fractions and enhanced oleic acid (18:1 N9) two-fold in three lipid fractions suggesting increased Delta9-desaturase activity while the content of several polyunsaturated fatty acids was reduced. In parallel, Delta9-Desaturase mRNA contents and enzyme activities in skeletal muscle were increased 10-fold, 75-fold, 2.6-fold and 7.7-fold after 2 and 5 days of glucose infusion, respectively.

CONCLUSION/INTERPRETATION

Our results suggest that long-term glucose oversupply induces a rapid increase in Delta9-desaturase expression and enzyme activity in skeletal muscle which leads to fast and specific changes in fatty acid metabolism possibly contributing to the insulin resistance in this animal model.

Enteral nutrition in the patient with diabetes mellitus

Diabetes mellitus is a serious and fairly common metabolic disorder that affects carbohydrate, protein and fat metabolism. Indications for nutritional support are no different for patients with diabetes than in any other patient group. The setting may be recovery from surgery or trauma and transition to solid food is anticipated, or, as a result of permanent injury or stroke, enteral feeding may be the permanent manner of nutrition delivery. Attention must be given to the selection of a macronutrient intake that will optimize blood glucose and lipid control. It is vital that blood glucose concentration be carefully monitored and that over- and underfeeding be avoided.

Clinical experience with modified enteral formulas for patients with diabetes

Standard tube-feeding formulas may not meet the specific nutritional needs of many patients with impaired glucose tolerance. In particular, standard enteral formulas often cause potentially dangerous increases in blood glucose levels. Clinical experience and studies to date have shown advantages of using disease-specific enteral formulas for these patients. Specialized formulas with increased fiber may improve glycemic control, although the concomitant increases in viscosity of these formulas may limit their usefulness for tube feeding. Glucerna, a specialized formula with low-carbohydrate, high-monounsaturated-fat content that has been enriched with a fiber source that permits tube feeding, has been shown to improve glycemic control and decrease the potential for complications. Appropriate tube feeding for patients with impaired glucose tolerance, however, extends beyond formula composition. Patients also require ongoing blood glucose monitoring, evaluation of gastric motility, and assessment of overall health and nutritional status.