Effect of acute hyperinsulinemia on fatty acid composition of serum lipids in non-insulin-dependent diabetics and healthy men

Free Radicals and Obesity-Related Chronic Inflammation Contrasted by Antioxidants: A New Perspective in Coronary Artery Disease

We are surrounded by factors called free radicals (FR), which attach to the molecules our body is made of, first among them the endothelium. Even though FR are to a certain extent a normal factor, nowadays we face an escalating increase in these biologically aggressive molecules. The escalating formation of FR is linked to the increased usage of man-made chemicals for personal care (toothpaste, shampoo, bubble bath, etc.), domestic laundry and dish-washer detergents, and also an ever wider usage of drugs (both prescription and over the counter), especially if they are to be used long-term (years). In addition, tobacco smoking, processed foods, pesticides, various chronic infectious microbes, nutritional deficiencies, lack of sun exposure, and, finally, with a markedly increasing impact, electromagnetic pollution (a terribly destructive factor), can increase the risk of cancer, as well as endothelial dysfunction, owing to the increased production of FR that they cause. All these factors create endothelial damage, but the organism may be able to repair such damage thanks to the intervention of the immune system supported by antioxidants. However, one other factor can perpetuate the state of inflammation, namely obesity and metabolic syndrome with associated hyperinsulinemia. In this review, the role of FR, with a special emphasis on their origin, and of antioxidants, is explored from the perspective of their role in causing atherosclerosis, in particular at the coronary level.

The zone diet: an anti-inflammatory, low glycemic-load diet

The Zone Diet was developed on the concept that the hormonal responses of macronutrients could be orchestrated to maintain key hormones within therapeutic zones to control inflammatory responses. In particular, the two hormonal systems that are directly affected by dietary macronutrients are (1) the insulin/glucagon axis and (2) eicosanoids. Each of these hormonal systems can have a significant impact on the inflammatory process. This hormonal approach to optimizing an anti-inflammatory diet has significant ramifications in treatment of those chronic diseases (obesity, type 2 diabetes, and cardiovascular disease) that are known to produce inflammatory responses. On the other hand, an inappropriate balance of macronutrients (especially high glycemic- load carbohydrates) can lead to increased inflammation. A primary example of this is the promotion of the United States Department of Agriculture's Food Guide Pyramid. Since its adoption, the prevalence of obesity and type 2 diabetes has risen substantially. Both conditions also demonstrate a significant increase in inflammatory markers. The purpose of this article is to review the historical factors that led to the development of the Zone Diet, to understand how the Zone Diet can alter inflammatory responses, and to review the published literature on its ability to affect hormonal and metabolic responses.

Anti-inflammatory nutrition as a pharmacological approach to treat obesity

Obesity is a multifactorial condition resulting from improper balances of hormones and gene expression induced by the diet. Obesity also has a strong inflammatory component that can be driven by diet-induced increases in arachidonic acid. The purpose of this paper is to discuss the molecular targets that can be addressed by anti-inflammatory nutrition. These molecular targets range from reduction of proinflammatory eicosanoids to the modulation of features of the innate immune system, such as toll-like receptors and gene transcription factors. From knowledge of the impact of these dietary nutrients on these various molecular targets, it becomes possible to develop a general outline of an anti-inflammatory diet that can offer a unique synergism with more traditional pharmacological approaches in treating obesity and its associated comorbidities.

Desaturase activities and metabolic control in type 2 diabetes

The aim of this study was to elucidate the effects of a poor glycemic control on fatty acid composition and desaturase activities in type 2 diabetic patients. Plasma phospholipid fatty acid composition and desaturase activities (estimated from fatty acid product to precursor ratios) were measured in 30 type 2 diabetic patients during poor metabolic control and after achieving a good metabolic control. Significant changes were recorded in the percentages of palmitic, stearic, dihomo-gamma-linolenic, docosatetraenoic and docosapentaenoic acid. The delta-5 desaturase activity was significantly higher with poor than with good metabolic control. The changes identified in plasma phospholipid fatty acid composition and the desaturase activity in type 2 diabetic patients go in the opposite direction to those described in similar conditions in type 1 diabetic patients and may be relevant to a better understanding of the role of metabolic control in the progression of chronic complications in type 2 diabetic 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.

Relation between plasma phospholipid saturated fatty acids and hyperinsulinemia

We determined whether plasma phospholipid fatty acid levels, an indicator of fatty acid composition in the diet, are associated with fasting serum insulin concentrations (a marker of insulin resistance). We examined cross-sectionally 4,304 middle-aged adults free of diabetes. Plasma fatty acid composition was quantified by gas chromatography. Fasting insulin was strongly and positively associated with the saturated fatty acid percentage in plasma phospholipids, moderately and inversely associated with the monounsaturated percentage, and not appreciably associated with the polyunsaturated percentage. Fasting insulin adjusted for age, smoking status, alcohol consumption, and sports participation, for example, was 29% higher in men and 33% higher in women per 1.9% greater level of saturated fatty acids (the interquartile range). After adjustment for body mass index (BMI) and other covariates, these estimates were 12% and 15% (P < .01 for the difference from zero). A 1.9% greater increment in saturated fatty acid level was also associated with a 2.4-fold higher odds of hyperinsulinemia (fasting insulin > or = 143.5 pmol/L). These data are consistent with studies showing that fatty acid composition of cell membranes modulates insulin action, and support the hypothesis that increased habitual saturated fat intake or a related dietary pattern is a risk factor for hyperinsulinemia.