Nutrition and skin. Collagen integrity: a dominant role for amino acids

Dietary Protein Deficit and Deregulated Autophagy: A New Clinico-diagnostic Perspective in Pathogenesis of Early Aging, Skin, and Hair Disorders

Background:

Diet has an important role to play in the well-being of human body.

Aims:

The study intends to establish the “hypothesis of conscious, selective, and self-destruction i.e., deregulated autophagy of skin and hair in low dietary protein scenario” by determining the facial profile, clinical presentation, and histopathological correlation of deficient protein intake and missing of meals in a tertiary care aesthetic skin institute.

Methods:

A total of 98 patients of skin- and hair-related complaints were enrolled in the study and a histopathological correlation was established by skin and scalp biopsies in high and low protein groups.

Results:

A significant number of subjects (68.4%) were taking less than half of the recommended daily allowance of proteins and faced problems like hair fall, acne, pigmentation, vitiligo, hirsutism, melasma, and premature aging. Subjects missing breakfast were found to have hypothyroidism, diffuse hairfall, autoimmune disorders like vitiligo, lichen planus, and alopecia areata. Histopathological images from submental area showed loose and fragmented collagen in high carbohydrate group in comparison to high protein group where thick, uniformly stained collagen bundles were found in dermis. Histopathology of scalp tissue showed chronic perifollicular inflammatory infiltrate and fibrosis in high carbohydrate group which was absent in histopathology specimen of high protein group. Patients taking early and nutrient-rich breakfast had higher mean protein intakes and less severe skin and hair problems suggesting a role of circadian rhythm as well.

Conclusion:

Dietary protein adequacy and early breakfast have significant role in preventing self-destruction or deregulated autophagy in trichology and cosmetic dermatology and may prevent various autoimmune, inflammatory, and metabolic diseases.

Efficacy of L-proline administration on the early responses during cutaneous wound healing in rats

Proline (Pro) plays a versatile role in cell metabolism and physiology. Pro and hydroxypro are major imino acids present in collagen, an important connective tissue protein, essential for wound healing, which is a primary response to tissue injury. This study explains the role of L-pro on cutaneous wound healing in rats when administered both topically and orally. Open excision wounds were made on the back of rats, and 200 μl (200 mg) of pro was administered topically and orally once daily to the experimental rats until the wounds healed completely. The control wounds were left untreated. Granulation tissues formed were removed after day 4 and 8 of post excision wounding, and biochemical parameters such as total protein, collagen, hexosamine, and uronic acid were estimated. Levels of enzymatic and non-enzymatic antioxidants such as catalase, superoxide dismutase, glutathione peroxidase, ascorbic acid, and reduced glutathione were evaluated along with lipid peroxides in the granulation tissues. Tensile strength and period of epithelialization were also measured. It was observed that the treated wounds healed very fast as evidenced by augmented rates of epithelialization and wound contraction, which was also confirmed by histological examinations. The results strappingly authenticate the beneficial effects of the topical administration of L-proline in the acceleration of wound healing than the oral administration and control.

Importance of amino acid composition to improve skin collagen protein synthesis rates in UV-irradiated mice

Skin collagen metabolism abnormalities induced by ultraviolet (UV) radiation are the major causes of skin photoaging. It has been shown that the one-time exposure of UV irradiation decreases procollagen mRNA expression in dermis and that chronic UV irradiation decreases collagen amounts and induces wrinkle formation. Amino acids are generally known to regulate protein metabolism. Therefore, we investigated the effects of UV irradiation and various orally administered amino acids on skin collagen synthesis rates. Groups of 4–5 male, 8-week-old HR-1 hairless mice were irradiated with UVB (66 mJ/cm²) twice every other day, then fasted for 16 h. The fractional synthesis rate (FSR; %/h) of skin tropocollagen was evaluated by incorporating l-[ring-²H₅]-phenylalanine. We confirmed that the FSR of dermal tropocollagen decreased after UVB irradiation. The FSR of dermal tropocollagen was measured 30 min after a single oral administration of amino acids (1 g/kg) to groups of 5–16 UVB-irradiated mice. Branched-chain amino acids (BCAA, 1.34 ± 0.32), arginine (Arg, 1.66 ± 0.39), glutamine (Gln, 1.75 ± 0.60), and proline (Pro, 1.48 ± 0.26) did not increase the FSR of skin tropocollagen compared with distilled water, which was used as a control (1.56 ± 0.30). However, essential amino acids mixtures (BCAA + Arg + Gln, BCAA + Gln, and BCAA + Pro) significantly increased the FSR (2.07 ± 0.58, 2.04 ± 0.54, 2.01 ± 0.50 and 2.07 ± 0.59, respectively). This result suggests that combinations of BCAA and glutamine or proline are important for restoring dermal collagen protein synthesis impaired by UV irradiation.

Topical application of dressing with amino acids improves cutaneous wound healing in aged rats

The principal goal in treating surgical and non-surgical wounds, in particular for aged skin, is the need for rapid closure of the lesion. Cutaneous wound healing processes involve four phases including an inflammatory response with the induction of pro-inflammatory cytokines. If inflammation develops in response to bacterial infection, it can create a problem for wound closure. Reduced inflammation accelerates wound closure with subsequent increased fibroblast function and collagen synthesis. On the contrary, prolonged chronic inflammation results in very limited wound healing. Using histological and immunohistochemical techniques, we investigated the effects of a new wound dressing called Vulnamin that contains four essential amino acids for collagen and elastin synthesis plus sodium ialuronate (Na-Ial), compared with Na-Ial alone, in closure of experimental cutaneous wounds of aged rats. Our results showed that the application of Vulnamin dressings modulated the inflammatory response with a reduction in the number of inflammatory cells and inducible nitric oxide synthase (iNOS) immunolocalisation, while increasing endothelial nitric oxide synthase (eNOS) and transforming growth factor-beta1 (TGF-beta1) immunolocalisation. Furthermore, the dressing increased the distribution density of fibroblasts and aided the synthesis of thin collagen fibers resulting in a reduction in healing time. The nutritive approach using this new wound dressing can provide an efficacious and safe strategy to accelerate wound healing in elderly subjects, simplifying therapeutic procedures and leading to an improved quality of life.