Measuring oral fatty acid thresholds, fat perception, fatty food liking, and papillae density in humans

Oral chemoreception of fatty acids and the association with diet and fatty food preferences may enable the identification of mechanisms involved with the development of obesity and why dietary changes may be difficult for many individuals.

Oral fatty acid sensitivity and dietary fat consumption

Lisa investigated the taste of fat and its influence on excess fat consumption and obesity. This research established that taste sensitivity to fat can be modulated by fat intake and may be used as an obesity prevention tool in the future.

Characterisation of lipase fatty acid selectivity using novel omega-3 pNP-acyl esters

 Lipases have applications for the industrial processing of lipids, including concentrating and/or modifying fish oil derived omega-3 fatty acids, widely used as nutritional supplement and functional food ingredients. A range of para-nitrophenol (pNP) acyl esters were synthesised as a means to rapidly screen lipases for fatty acid selectivity using spectrophotometric detection. The chosen esters were based primarily on the most abundant fatty acids present in anchovy and tuna oils. pNP derivatives of C16:1 n-7, C18:1 n-9 (OA), C18:2 n-6 (LA), C18:3 n-3 (ALA), C20:5 n-3 (EPA) and C22:6 n-3 (DHA) were synthesised. Storage stability of these pNP derivatives was shown to be at least 6 months and all pNP derivatives, including those of EPA and DHA, were shown to be stable throughout the conditions of the assay. We applied the new assay substrates for the determination of fatty acid selectivity of five widely utilised lipases. Results showed that the lipase from Candida rugosa was the most selective in terms of omega-3 specificity, preferentially hydrolysing all other medium– long chain substrates. Lipases from Rhizomucor miehei and Thermomyces lanuginosa also showed selectivity, with a significant preference for saturated fatty acids. Candida Antarctica lipase B and Aspergillus niger lipase were the least selective.

Endurance training in obese humans improves glucose tolerance and mitochondrial fatty acid oxidation and alters muscle lipid content

Muscle fatty acid (FA) metabolism is impaired in obesity and insulin resistance, reflected by reduced rates of FA oxidation and accumulation of lipids. It has been suggested that interventions that increase FA oxidation may enhance insulin action by reducing these lipid pools. Here, we examined the effect of endurance training on rates of mitochondrial FA oxidation, the activity of carnitine palmitoyltransferase I (CPT I), and the lipid content in muscle of obese individuals and related these to measures of glucose tolerance. Nine obese subjects completed 8 wk of moderate-intensity endurance training, and muscle biopsies were obtained before and after training. Training significantly improved glucose tolerance, with a reduction in the area under the curve for glucose (P< 0.05) and insulin (P = 0.01) during an oral glucose tolerance test. CPT I activity increased 250% (P = 0.001) with training and became less sensitive to inhibition by malonyl-CoA. This was associated with an increase in mitochondrial FA oxidation (+120%, P < 0.001). Training had no effect on muscle triacylglycerol content; however, there was a trend for training to reduce both the total diacylglcyerol (DAG) content (−15%, P = 0.06) and the saturated DAG-FA species (−27%, P = 0.06). Training reduced both total ceramide content (−42%, P = 0.01) and the saturated ceramide species (−32%, P < 0.05). These findings suggest that the improved capacity for mitochondrial FA uptake and oxidation leads not only to a reduction in muscle lipid content but also a to change in the saturation status of lipids, which may, at least in part, provide a mechanism for the enhanced insulin action observed with endurance training in obese individuals.

Cytokine regulation of skeletal muscle fatty acid metabolism: effect of interleukin-6 and tumor necrosis factor-α

IL-6 and TNF-α have been associated with insulin resistance and type 2 diabetes. Furthermore, abnormalities in muscle fatty acid (FA) metabolism are strongly associated with the development of insulin resistance. However, few studies have directly examined the effects of either IL-6 or TNF-α on skeletal muscle FA metabolism. Here, we used a pulse-chase technique to determine the effect of IL-6 (50-5,000 pg/ml) and TNF-α (50-5,000 pg/ml) on FA metabolism in isolated rat soleus muscle. IL-6 (5,000 pg/ml) increased exogenous and endogenous FA oxidation by ≃50% (P < 0.05) but had no effect on FA uptake or incorporation of FA into endogenous lipid pools. In contrast, TNF-α had no effect on FA oxidation but increased FA incorporation into diacylglycerol (DAG) by 45% (P < 0.05). When both IL-6 (5,000 pg/ml) and insulin (10 mU/ml) were present, IL-6 attenuated insulin's suppressive effect on FA oxidation, increasing exogenous FA oxidation (+37%, P < 0.05). Furthermore, in the presence of insulin, IL-6 reduced the esterification of FA to triacylglycerol by 22% (P < 0.05). When added in combination with IL-6 or leptin (10 μg/ml), the TNF-α-induced increase in DAG synthesis was inhibited. In conclusion, the results demonstrate that IL-6 plays an important role in regulating fat metabolism in muscle, increasing rates of FA oxidation, and attenuating insulin's lipogenic effects. In contrast, TNF-α had no effect on FA oxidation but increased FA incorporation into DAG, which may be involved in the development of TNF-α-induced insulin resistance in skeletal muscle.

Greater effect of diet than exercise training on the fatty acid profile of rat skeletal muscle

We determined the interaction of diet and exercise-training intensity on membrane phospholipid fatty acid (FA) composition in skeletal muscle from 36 female Sprague-Dawley rats. Animals were randomly divided into one of two dietary conditions: high-carbohydrate (64.0% carbohydrate by energy, n = 18) or high fat (78.1% fat by energy, n = 18). Rats in each diet condition were then allocated to one of three subgroups: control, which performed no exercise training; low-intensity (8 m/min) treadmill run training; or high-intensity (28 m/min) run training. All exercise-trained rats ran 1,000 m/session, 4 days/wk for 8 wk and were killed 48 h after the last training bout. Membrane phospholipids were extracted, and FA composition was determined in the red and white vastus lateralis muscles, Diet exerted a major influence on phospholipid FA composition, with the high-fat diet being associated with a significantly (P < 0.01) elevated ratio of n-6/n-3 FA for both red (2.7-3.2 vs. 1.0-1.1) and white vastus lateralis muscle (2.5-2.9 vs. 1.2). In contrast, alterations in FA composition as a result of either exercise-training protocol were only minor in comparison. We conclude that, under the present experimental conditions, a change in the macronutrient content of the diet was a more potent modulator of skeletal muscle membrane phospholipid FA composition compared with either low- or high-intensity treadmill exercise training.

Rapid discrimination and determination of polyunsaturated fatty acid composition in marine oils by FTIR Spectroscopy and Multivariate Data Analysis

A rapid analytical approach for discrimination and quantitative determination of polyunsaturated fatty acid (PUFA) contents, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), in a range of oils extracted from marine resources has been developed by using attenuated total reflection Fourier transform infrared spectroscopy and multivariate data analysis. The spectral data were collected without any sample preparation; thus, no chemical preparation was involved, but data were rather processed directly using the developed spectral analysis platform, making it fast, very cost effective, and suitable for routine use in various biotechnological and food research and related industries. Unsupervised pattern recognition techniques, including principal component analysis and unsupervised hierarchical cluster analysis, discriminated the marine oils into groups by correlating similarities and differences in their fatty acid (FA) compositions that corresponded well to the FA profiles obtained from traditional lipid analysis based on gas chromatography (GC). Furthermore, quantitative determination of unsaturated fatty acids, PUFAs, EPA and DHA, by partial least square regression analysis through which calibration models were optimized specifically for each targeted FA, was performed in both known marine oils and totally independent unknown n - 3 oil samples obtained from an actual commercial product in order to provide prospective testing of the developed models towards actual applications. The resultant predicted FAs were achieved at a good accuracy compared to their reference GC values as evidenced through (1) low root mean square error of prediction, (2) good coefficient of determination close to 1 (i.e., R 2≥ 0.96), and (3) the residual predictive deviation values that indicated the predictive power at good and higher levels for all the target FAs. © 2014 Springer Science+Business Media New York.

FTIR microspectroscopy for rapid screening and monitoring of polyunsaturated fatty acid production in commercially valuable marine yeasts and protists

The increase in polyunsaturated fatty acid (PUFA) consumption has prompted research into alternative resources other than fish oil. In this study, a new approach based on focal-plane-array Fourier transform infrared (FPA-FTIR) microspectroscopy and multivariate data analysis was developed for the characterisation of some marine microorganisms. Cell and lipid compositions in lipid-rich marine yeasts collected from the Australian coast were characterised in comparison to a commercially available PUFA-producing marine fungoid protist, thraustochytrid. Multivariate classification methods provided good discriminative accuracy evidenced from (i) separation of the yeasts from thraustochytrids and distinct spectral clusters among the yeasts that conformed well to their biological identities, and (ii) correct classification of yeasts from a totally independent set using cross-validation testing. The findings further indicated additional capability of the developed FPA-FTIR methodology, when combined with partial least squares regression (PLSR) analysis, for rapid monitoring of lipid production in one of the yeasts during the growth period, which was achieved at a high accuracy compared to the results obtained from the traditional lipid analysis based on gas chromatography. The developed FTIR-based approach when coupled to programmable withdrawal devices and a cytocentrifugation module would have strong potential as a novel online monitoring technology suited for bioprocessing applications and large-scale production.

Fatty acid-specific alterations in leptin, PPARα, and CPT-1 gene expression in the rainbow trout

It is known that fatty acids (FA) regulate lipid metabolism by modulating the expression of numerous genes. In order to gain a better understanding of the effect of individual FA on lipid metabolism related genes in rainbow trout (Oncorhynchus mykiss), an in vitro time-course study was implemented where twelve individual FA (butyric 4:0; caprylic 8:0; palmitic (PAM) 16:0; stearic (STA) 18:0; palmitoleic16:1n-7; oleic 18:1n-9; 11-cis-eicosenoic 20:1n-9; linoleic (LNA) 18:2n-6; α-linolenic (ALA) 18:3n-3; eicosapentenoic (EPA) 20:5n-3; docosahexaenoic (DHA) 22:6n-3; arachidonic (ARA) 20:4n-6) were incubated in rainbow trout liver slices. The effect of FA administration over time was evaluated on the expression of leptin, PPARα and CPT-1 (lipid oxidative related genes). Leptin mRNA expression was down regulated by saturated fatty acids (SFA) and LNA, and was up regulated by monounsaturated fatty acids (MUFA) and long chain PUFA, whilst STA and ALA had no effect. PPARα and CPT-1mRNA expression were up regulated by SFA, MUFA, ALA, ARA and DHA; and down regulated by LNA and EPA. These results suggest that there are individual and specific FA induced modifications of leptin, PPARα and CPT-1 gene expression in rainbow trout, and it is envisaged that such results may provide highly valuable information for future practical applications in fish nutrition.