Dietary lipid is largely deposited in skin and rapidly affects insulating properties.

Skin has been shown to be a regulatory hub for energy expenditure and metabolism: mutations of skin lipid metabolism enzymes can change the rate of thermogenesis and susceptibility to diet-induced obesity. However, little is known about the physiological basis for this function. Here we show that the thermal properties of skin are highly reactive to diet: within three days, a high fat diet reduces heat transfer through skin. In contrast, a dietary manipulation that prevents obesity accelerates energy loss through skins. We found that skin was the largest target in a mouse body for dietary fat delivery, and that fat was assimilated both by epidermis and by dermal white adipose tissue. Dietary triglyceride acyl groups persist in skin for weeks after feeding. Using multi-modal lipid profiling, we have implicated both keratinocytes and sebocytes in the altered lipids which correlate with thermal function. In response to high fat feeding, wax diesters and ceramides accumulate, and triglycerides become more saturated. In contrast, in response to the dramatic loss of adipose tissue that accompanies restriction of the branched chain amino acid isoleucine, skin becomes highly heat-permeable: skins shows limited uptake of dietary lipids and editing of wax esters, and acquires a signature of depleted signaling lipids, which include the acyl carnitines and lipid ethers. We propose that skin should be routinely included in physiological studies of lipid metabolism, given the size of the skin lipid reservoir and its adaptable functionality.

Variants in ALDH1A2 reveal an anti-inflammatory role for retinoic acid and a new class of disease-modifying drugs in osteoarthritis.

More than 40% of individuals will develop osteoarthritis (OA) during their lifetime, yet there are currently no licensed disease-modifying treatments for this disabling condition. Common polymorphic variants in ALDH1A2, which encodes the key enzyme for synthesis of all-trans retinoic acid (atRA), are associated with severe hand OA. Here, we sought to elucidate the biological significance of this association. We first confirmed that ALDH1A2 risk variants were associated with hand OA in the U.K. Biobank. Articular cartilage was acquired from 33 individuals with hand OA at the time of routine hand OA surgery. After stratification by genotype, RNA sequencing was performed. A reciprocal relationship between ALDH1A2 mRNA and inflammatory genes was observed. Articular cartilage injury up-regulated similar inflammatory genes by a process that we have previously termed mechanoflammation, which we believe is a primary driver of OA. Cartilage injury was also associated with a concomitant drop in atRA-inducible genes, which were used as a surrogate measure of cellular atRA concentration. Both responses to injury were reversed using talarozole, a retinoic acid metabolism blocking agent (RAMBA). Suppression of mechanoflammation by talarozole was mediated by a peroxisome proliferator-activated receptor gamma (PPARγ)-dependent mechanism. Talarozole was able to suppress mechano-inflammatory genes in articular cartilage in vivo 6 hours after mouse knee joint destabilization and reduced cartilage degradation and osteophyte formation after 26 days. These data show that boosting atRA suppresses mechanoflammation in the articular cartilage in vitro and in vivo and identifies RAMBAs as potential disease-modifying drugs for OA.

A software program designed to educate patients on age-related skin changes of facial and exposed extrafacial regions: the results of a validation study.

BACKGROUND: A software program called "HOYS" has been developed to depict various aspects and degrees of aging at 35 constituent subregions of seven distinct facial or exposed extrafacial regions. This program is underpinned by five-point photonumeric Likert scales characterizing skin surface and volume changes across five decades for each of the 35 subregions, and features an interactive skin-age assessment with a treatment-prioritization tool. In this study, the reliability and reproducibility of these scales was evaluated. METHODS: Eleven physicians and 19 non-physicians participated in this study. The five images from each of the 35 Likert scales in the HOYS program were shown on a total of 43 display boards, with selected subregions presented at rest or with movement, consistent with this program. Each image was randomly labeled between "A-E," corresponding to a range of skin ages by decade from 20-69 years. Each rater was asked to rank these images from youngest to oldest (or least to most severe deficit) for each scale and to repeat this exercise 2 hours later, with the intra- and inter-rater reliability evaluated. The raters were also asked to estimate the age of a single randomly allocated image on each scale for the purposes of internal validation. RESULTS: The overall inter-rater reliability of the raters was high at the first ranking session (weighted kappa: 0.78; 95% confidence intervals [95% CI]: 0.77-0.79) and this was confirmed when repeated 2 hours later (0.82; 95% CI: 0.81-0.83), with an intra-rater reliability of 0.76 (95% CI: 0.75-0.77). There was no significant difference in the physicians' and non-physicians' rankings. The raters also accurately estimated the actual age of the single randomly allocated image from each of the 43 stations (0.72; 95% CI: 0.70-0.74). A very similar pattern was observed when the ratings of a constituent of one of the seven regions, the perioral/lower face, were analyzed for expounding purposes. CONCLUSION: The high reliability and reproducibility of the ranking in this validation study suggests that the five-point photonumeric Likert scales used in the HOYS program are an accurate depiction of age-related changes over five decades in the seven facial and extrafacial regions represented in this program, from the ages of 20-69 years.