Dietary CLA and DHA modify skin properties in mice

Repeated restraint stress modifies fatty acid and amino acid metabolism in the mouse skin

In modern society, stress caused by relationships and emotions is one of the greatest social problems. Similar to humans, domestic and captive animals live under various stresses. Several stresses have been associated with skin disorders, such as atopic dermatitis, but there is a lack of reliable and objective indicators for the characterization of this association. This study aimed to define the changes in fatty acid composition and amino acid concentration in the skin following repeated restraint stress in ICR mice. Mice subjected to 30 min of daily restraint stress for 8 days showed changes in the composition of saturated fatty acids, such as an increase in palmitic acid content, which are the substrates of Δ-9 desaturase. Conversely, unsaturated fatty acids decreased with stress treatment, which appeared to be a result of these fatty acids being the substrate of Δ-6 desaturase. Changes in fatty acid composition after stress treatment may be one of the factors that cause skin inflammation. The water-retention capacity may have been lowered by stress treatment because histidine and leucine, which are natural moisturizing factors, were significantly decreased. The collagen content in the skin gradually decreased after repeated stress treatment. Our results indicate that repeated restraint stress may impact skin health through changes in both the fatty acid composition and amino acid concentration in mice.

A high-fat diet reduces ceramide synthesis by decreasing adiponectin levels and decreases lipid content by modulating HMG-CoA reductase and CPT-1 mRNA expression in the skin

SCOPE

Molecules involved in skin function are greatly affected by nutritional conditions. However, the mechanism linking high-fat (HF) diets with these alterations is not well understood. This study aimed to investigate the molecular changes in skin function that result from HF diets.

METHODS AND RESULTS

Sprague-Dawley rats were fed HF diets for 28 days. The skin levels of ceramide, lipids and mRNAs involved in lipid metabolism were evaluated using TLC, oil red O staining and quantitative PCR, respectively. The serum adiponectin concentration was determined by ELISA. HF diets led to reduced ceramide levels and lowered skin lipid content. They also decreased mRNA levels of serine palmitoyltransferase (SPT) and 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase in the skin and those of peroxisome proliferator-activated receptor-α -PPAR-α), which upregulates SPT and HMG-CoA reductase expression. The HF diets reduced the serum concentration of adiponectin, which acts upstream of PPAR-α. Finally, these diets led to increased mRNA levels of carnitine palmitoyltransferase-1, the rate-limiting enzyme that acts in β-oxidation.

CONCLUSION

Our study suggests that HF diets reduce ceramide and lipid synthesis in the skin by reducing levels of SPT and HMG-CoA reductase through lowered adiponectin and PPAR-α activity. Additionally, they decrease lipid content by enhancing β-oxidation.

Modification of skin composition by conjugated linoleic acid alone or with combination of other fatty acids in mice

The effects of conjugated linoleic acid (CLA), γ-linolenic acid (GLA), linoleic acid (LA), and their combinations, on skin composition in mice were investigated. Mice (8 weeks old) were orally administered with either LA, GLA, CLA, LA + GLA, LA + CLA, or CLA + GLA for 4 weeks. Then, the skin was analysed for triacylglycerol content, fatty acid composition and collagen content. Additionally, thicknesses of the dermis layer and subcutaneous tissue layer, and the size and number of adipocytes were measured histologically. The skin fatty acid composition was modified depending upon the fatty acid composition of supplemented oils. In each oil-alone group, skin triacylglycerol content was the highest in LA, followed by GLA and CLA treatments. Combinations with CLA had a similar triacylglycerol content compared with the CLA-alone group. No significant changes in collagen content were observed among any treatments. The effects on subcutaneous thickness were similar to the results obtained in the triacylglycerol contents, where groups supplemented with CLA alone or other fatty acids had significantly thinner subcutaneous tissue compared with the LA-alone group. However, no significant difference was detected in the thickness of the dermis layers. The number of adipocytes was highest in the LA + GLA group and tended to be reduced by CLA with or without the other fatty acids. These results suggest that CLA alone or in combination with other fatty acids strongly modifies skin composition in mice.