Saturated fatty acids, linseed components and high amylose wheat in attenuation of diet-induced metabolic syndrome

Saturated fatty acids, linseed components and high amylose wheat in attenuation of diet-induced metabolic syndrome

Metabolic syndrome is a syndrome characterised by central obesity, dyslipidaemia, hypertension, fatty liver disease and insulin resistance that ultimately raises the risk of heart disease, diabetes, stroke, cancers and osteoarthritis. In combating metabolic syndrome, lifestyle changes are considered the most important initial steps which include a healthy, well-balanced diet and increased physical activity. Enrichment of beneficial fatty acids and incorporation of functional foods and bioactive nutrients are part of healthy dietary regimes in treating metabolic syndrome. These strategies provide options other than drug therapies that may cause adverse effects. Nevertheless, the effectiveness of these foods or bioactive nutrients in treating metabolic syndrome has yet to be fully explored. Therefore, in this thesis, I examined the physiological effects of individual saturated fatty acids (lauric, myristic, palmitic and stearic acid), linseed components (lignans, raw linseed and defatted linseed) and
high amylose wheat (5% and 20%) using a validated diet-induced rat model of cardiovascular, liver and metabolic changes mimicking most of the changes in the human metabolic syndrome.

Male Wistar rats fed with either diet containing 20% of lauric, myristic, palmitic, or stearic acid or corn-starch or high-carbohydrate, high-fat diet for 16 weeks
showed that longer-chain saturated fatty acids (myristic, palmitic and stearic) and the mixture of stearic and trans fats in beef tallow produced obesity, in contrast to rats
treated with lauric acid that exhibited low total fat mass, abdominal circumference and visceral adiposity index. Lauric acid supplemented rats also showed a normal
cardiovascular and hepatic structure compared to other saturated fatty acids. This study suggests that replacing beef tallow with stearic and palmitic acids would show small
improvements but replacement with lauric and possibly myristic acids in human diets would markedly attenuate the development of metabolic syndrome.

Linseed is a rich source of plant lignans such as secoisolariciresinol diglucoside, as well as dietary fibre. Supplementation of lignan (0.03%) and defatted
linseed (3%) in a high-carbohydrate, high-fat diet for eight weeks lowered body weight gain, total fat mass, improved cardiovascular functions, reduced hepatic steatosis and altered metabolic profiles, which can be regarded as beneficial to health, whereas raw
linseed (5%) exacerbated adiposity with no changes in other metabolic biomarkers except for reduced systolic blood pressure. This study suggests that lignan and dietary
fibre in defatted linseed could reduce the symptoms of metabolic syndrome. In contrast, positive physiological effects of raw linseed diminish possibly due to the
properties of raw linseed that may pass through the intestine undigested, which means the nutritional benefits are unable to be realised. Another functional food described in this thesis is high amylose wheat flour.
In this study, two dosages (5% and 20%) of high amylose wheat flour were supplemented in high-carbohydrate, high-fat diet for 8 weeks. Rats fed with 5% high amylose wheat flour showed no changes in the metabolic parameters. However, highcarbohydrate, high-fat diet-fed rats fed 20% high amylose wheat flour showed reduced body fat mass and increased lean mass despite no change in the body weight. The addition of 20% high amylose wheat in the diet was also associated with better glycaemic control, decreased insulin and leptin concentrations with cardioprotective
and hepatoprotective effects. These effects are probably due to the increased resistant starch content in high amylose wheat, thus ameliorating the risk of developing
metabolic syndrome.

The studies in this thesis provided evidence that not all saturated fatty acids are equal, with lauric acid producing fewer pathophysiological changes in most parameters than other saturated fatty acids in this model of diet-induced metabolic syndrome. Studies from linseed components and high amylose wheat clearly indicate that these foods or food components have the potential to reverse most of the risk factors associated with metabolic syndrome. The most likely mechanisms of these food or food components are through the cardioprotective and hepatoprotective effects
produced by anti-inflammatory responses.