Clinical research results of vitamin D supplementation in the improvement of prediabetes remain controversial. Accordingly, a literature search was conducted of PubMed, Embase (Ovid), and Web of Science prior to 9 November 2021. Randomized controlled studies reported that the following indicators were included: body mass index (BMI), fasting blood glucose (FBG), 2 h oral glucose tolerance test plasma glucose (2h-PG), hemoglobin A1c (HbA1c), insulin resistance by homeostasis model assessment (HOMA-IR), homeostasis model assessment of β-cell function (HOMA-B), and fasting insulin (FINS). Twenty-nine articles (N = 3792) were included in the present meta-analysis. Intriguingly, vitamin D supplementation resulted in a vast improvement in FBG (standardized mean difference (SMD) = −0.38; 95%CI: −0.59, −0.16), HbA1c (SMD = −0.14; 95%CI: −0.22, −0.06) and FINS (SMD = 0.18; 95%CI: −0.26, −0.09), but not in other outcomes. However, preferred changes were observed in subgroups, as follows: Asia (SMD_2h-PG = −0.25, 95%CI: −0.45, −0.04), study duration ≥1 year (SMD_HOMA-IR = −0.44, 95%CI: −0.81, −0.06) (SMD_HOMA-B = 0.34, 95%CI: 0.01, 0.66), baseline 25(OH)D < 50 nmol/L (SMD_2h-PG = −0.23, 95%CI: −0.39, −0.06), and baseline 25(OH)D ≥ 50 nmol/L (SMD_HOMA-IR = −0.50, 95%CI: −0.96, −0.03). In conclusion, oral supplementation of vitamin D has shown better effects in improving FBG, HbA1c, and FINS compared with controls among prediabetics; long-term vitamin D supplementation could have additional effects in participants with vitamin D deficiency for 2h-PG, HOMA-IR, and HOMA-B.

Alzheimer’s disease (AD) is characterized by the deposition of senile plaques (SPs) and the formation of neurofibrillary tangles (NTFs), as well as neuronal dysfunctions in the brain, but in fact, patients have shown a sustained disease progression for at least 10 to 15 years before these pathologic biomarkers can be detected. Consequently, as the most common chronic neurological disease in the elderly, the challenge of AD treatment is that it is short of effective biomarkers for early diagnosis. The protein quality control system is a collection of cellular pathways that can recognize damaged proteins and thereby modulate their turnover. Abundant evidence indicates that the accumulation of abnormal proteins in AD is closely related to the dysfunction of the protein quality control system. In particular, it is the synthesis, degradation, and removal of essential biological components that have already changed in the early stage of AD, which further encourages us to pay more attention to the protein quality control system. The review mainly focuses on the endoplasmic reticulum system (ERS), autophagy–lysosome system (ALS) and the ubiquitin–proteasome system (UPS), and deeply discusses the relationship between the protein quality control system and the abnormal proteins of AD, which can not only help us to understand how and why the complex regulatory system becomes malfunctional during AD progression, but also provide more novel therapeutic strategies to prevent the development of AD.

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a prevalent global health concern. Although pharmacotherapies such as Resmetirom and semaglutide have recently gained approval by FDA/EMEA, therapeutic options remain limited, necessitating the exploration of novel natural compounds. Our previous research indicated that lycopene exerts protective effects against MASLD; however, its underlying molecular mechanisms remain incompletely understood. The present study aimed to investigate whether lycopene alleviates MASLD by modulating mitophagy, with a focus on the PINK1/Parkin pathway. C57BL/6J mice were fed with high-fat diet for 12 weeks to induce MASLD and daily gavage of lycopene (10/40 mg/kg). In vitro, AML12 cells were treated with lycopene and Mdivi-1 to assess the role of PINK1/Parkin-mediated mitophagy against lipid accumulation, oxidative stress, and apoptosis. The results found that lycopene supplementation significantly ameliorated HFD-induced weight gain, dyslipidemia, hepatic steatosis, pathological liver injury, and elevated serum liver enzymes. It reduced hepatic reactive oxygen species (ROS) overproduction and suppressed the mitochondrial apoptotic pathway, as evidenced by decreased cytochrome c release and caspase cascade activation. Concurrently, lycopene restored ATP levels and mitochondrial membrane potential, improved ultrastructural integrity, and balanced mitochondrial dynamics by downregulating DRP1 and upregulating MFN2 and OPA1. Crucially, lycopene activated PINK1/Parkin-mediated mitophagy, leading to an increased LC3-II/LC3-I ratio and Beclin1 expression, alongside decreased levels of mitochondrial proteins TOM20 and COX IV. In vitro, the lycopene partially reversed the exacerbating effects of Mdivi-1 on lipid accumulation, ROS generation, apoptosis, and the suppression of the PINK1/Parkin pathway. Collectively, lycopene ameliorates MASLD by activating PINK1/Parkin-mediated mitophagy and improving mitochondrial homeostasis, thereby reducing hepatic lipid accumulation and attenuating hepatocyte apoptosis.