Skin photoaging is mainly induced by ultraviolet (UV) irradiation and its manifestations include dry skin, coarse wrinkle, irregular pigmentation, and loss of skin elasticity. Dietary supplementation of nutraceuticals with therapeutic and preventive effects against skin photoaging has recently received increasing attention. This article aims to review the research progress in the cellular and molecular mechanisms of UV-induced skin photoaging. Subsequently, the beneficial effects of dietary components on skin photoaging are discussed. The photoaging process and the underlying mechanisms are complex. Matrix metalloproteinases, transforming growth factors, skin adipose tissue, inflammation, oxidative stress, nuclear and mitochondrial DNA, telomeres, microRNA, advanced glycation end products, the hypothalamic–pituitary–adrenal axis, and transient receptor potential cation channel V are key regulators that drive the photoaging-associated changes in skin. Meanwhile, mounting evidence from animal models and clinical trials suggests that various food-derived components attenuate the development and symptoms of skin photoaging. The major mechanisms of these dietary components to alleviate skin photoaging include the maintenance of skin moisture and extracellular matrix content, regulation of specific signaling pathways involved in the synthesis and degradation of the extracellular matrix, and antioxidant capacity. Taken together, the ingestion of food-derived functional components could be an attractive strategy to prevent skin photoaging damage.

Previous studies have reported the therapeutic effects of oleuropein (OP) consumption on the early stage of type 2 diabetes. However, the efficacy of OP on the advanced stage of type 2 diabetes has not been investigated, and the relationship between OP and intestinal flora has not been studied. Therefore, in this study, to explore the relieving effects of OP intake on the advanced stage of type 2 diabetes and the regulatory effects of OP on intestinal microbes, diabetic db/db mice (17-week-old) were treated with OP at the dose of 200 mg/kg for 15 weeks. We found that OP has a significant effect in decreasing fasting blood glucose levels, improving glucose tolerance, lowering the homeostasis model assessment–insulin resistance index, restoring histopathological features of tissues, and promoting hepatic protein kinase B activation in db/db mice. Notably, OP modulates gut microbiota at phylum level, increases the relative abundance of Verrucomicrobia and Deferribacteres, and decreases the relative abundance of Bacteroidetes. OP treatment increases the relative abundance of Akkermansia, as well as decreases the relative abundance of Prevotella, Odoribacter, Ruminococcus, and Parabacteroides at genus level. In conclusion, OP may ameliorate the advanced stage of type 2 diabetes through modulating the composition and function of gut microbiota. Our findings provide a promising therapeutic approach for the treatment of advanced stage type 2 diabetes.

Diabetes has become one of the biggest non-communicable diseases and threatens human health worldwide. The management of diabetes is a complex and multifaceted process including drug therapy and lifestyle interventions. Dietary components are essential for both diabetes management and health and survival of trillions of the gut microbiota (GM). Herein, we will discuss the relationship between diets and GM, the mechanism linking diabetes and gut dysbiosis, and the effects of dietary components (nutrients, phytochemicals, probiotics, food additives, etc.) on diabetes from the perspective of modulating GM. The GM of diabetic patients differs from that of health individuals and GM disorder contributes to the onset and maintenance of diabetes. Studies in humans and animal models consolidate that dietary component is a key regulator of diabetes and increasing evidence suggests that the alteration of GM plays a salient role in dietary interventions for diabetes. Given that diabetes is a major public health issue, especially that diabetes is linked with a high risk of mortality from COVID-19, this review provides compelling evidence for that targeting GM by dietary components is a promising strategy, and offers new insights into potential preventive or therapeutic approaches (dietary and pharmacological intervention) for the clinical management of diabetes. Graphical Abstract

Odorant receptors (ORs) and taste receptors (TRs) are expressed primarily in the nose and tongue in which they transduce electrical signals to the brain. Advances in deciphering the dietary component-sensing mechanisms in the nose and tongue prompted research on the role of gut chemosensory cells. Acting as the pivotal interface between the body and dietary cues, gut cells “smell” and “taste” dietary components and metabolites by taking advantage of chemoreceptors—ORs and TRs, to maintain physiological homeostasis. Here, we reviewed this novel field, highlighting the latest discoveries pertinent to gut ORs and TRs responding to dietary components, their impacts on gut hormone secretion, and the mechanisms involved. Recent studies indicate that gut cells sense dietary components including fatty acid, carbohydrate, and phytochemical by activating relevant ORs, thereby modulating GLP-1, PYY, CCK, and 5-HT secretion. Similarly, gut sweet, umami, and bitter receptors can regulate the gut hormone secretion and maintain homeostasis in response to dietary components. A deeper understanding of the favorable influence of dietary components on gut hormone secretion via gut ORs and TRs, coupled with the facts that gut hormones are involved in diverse physiological or pathophysiological phenomena, may ultimately lead to a promising treatment for various human diseases. Graphical Abstract