CYB5R3 overexpression exhibits sexual dimorphism: Mitochondrial and metabolic adaptations in transgenic female mice during calorie restriction.

There is a pressing need to develop new strategies for enhancing health in the elderly and preventing the rise in age-related diseases. Calorie restriction without malnutrition (CR) stands among the different antiaging interventions. Lifelong CR leads to increased expression and activity of plasma membrane CYB5R3, and male mice overexpressing CYB5R3 exhibit some beneficial adaptations that are also seen with CR. However, the mechanisms involved in both interventions could be independent since key aspects of energy metabolism and tissue lipid profile do not coincide, and many of the changes induced by CR in mitochondrial abundance and dynamics in the liver and skeletal muscle could be counteracted by CYB5R3 overexpression. In this study, we sought to elucidate the impact of CR on key markers of metabolic status, mitochondrial function, and pro-oxidant/antioxidant balance in transgenic (TG) female mice overexpressing CYB5R3 compared to their WT littermates. In females fed ad libitum, CYB5R3 overexpression decreased fat mass, led to a preferred utilization of fatty acids as an energy source, upregulated key antioxidant enzymes, and boosted respiration both in skeletal muscle and liver mitochondria, supporting that CYB5R3 overexpression is phenotypic closer to CR in females than in males. Whereas some markers of mitochondrial biogenesis and dynamics were found decreased in TG females on CR, as also found for the levels of Estrogen Receptor α, mitochondrial abundance and activity were maintained both in skeletal muscle and in liver. Our results reveal overlapping metabolic adaptations resulting from the overexpression of CYB5R3 and CR in females, but a specific crosstalk occurs when both interventions are combined, differing from the adaptations observed in TG males.

Sex-specific metabolic adaptations in transgenic mice overexpressing cytochrome b5 reductase-3.

Cytochrome b5 reductase 3 (CYB5R3) activates respiratory metabolism in cellular systems and exerts a prolongevity action in transgenic mice overexpressing this enzyme, mimicking some of the beneficial effects of calorie restriction. The aim of our study was to investigate the role of sex on metabolic adaptations elicited by CYB5R3 overexpression, and how key markers related with mitochondrial function are modulated in skeletal muscle, one of the major contributors to resting energy expenditure. Young CYB5R3 transgenic mice did not exhibit the striking adaptations in carbon metabolism previously detected in older animals. CYB5R3 was efficiently overexpressed and targeted to mitochondria in skeletal muscle from transgenic mice regardless sex. Overexpression significantly elevated NADH in both sexes, although differences were not statistically significant for NAD+, and increased the abundance of cytochrome c and the fission protein DRP-1 in females but not in males. Moreover, while mitochondrial biogenesis and function markers (as TFAM, NRF-1 and cleaved SIRT3) were markedly upregulated by CYB5R3 overexpression in females, a downregulation was observed in males. Ultrastructural changes were also highlighted, with an increase in the number of mitochondria per surface unit, and in the size of intermyofibrillar mitochondria in transgenic females compared with their wild-type controls. Our results support that CYB5R3 overexpression upregulates markers consistent with enhanced mitochondrial biogenesis and function, and increases mitochondrial abundance in skeletal muscle, producing most of these potentially beneficial actions in females.

Preclinical Characterization of Pharmacologic NAD+ Boosting as a Promising Therapeutic Approach in Rheumatoid Arthritis.

OBJECTIVE: We analyzed NAD+ metabolism in patients with rheumatoid arthritis (RA), its association with disease activity and clinical outcomes of RA, and the therapeutic potential of pharmacologic NAD+ boosting. METHODS: Our study included 253 participants. In the first cohort, comprising 153 RA patients and 56 healthy donors, we assessed NAD+ levels and NAD+ -related gene pathways. We analyzed 92 inflammatory molecules by proximity extension assay. In the second cohort, comprising 44 RA patients starting anti-tumor necrosis factor (anti-TNF) drugs, we evaluated changes in NAD+ levels and their association with clinical response after 3 months. Mechanistic studies were performed ex vivo on peripheral blood mononuclear cells (PBMCs) from patients with RA to test the beneficial effects of NAD+ boosters, such as nicotinamide and nicotinamide riboside. RESULTS: Reduced NAD+ levels were found in RA samples, in line with altered activity and expression of genes involved in NAD+ consumption (sirtuins, poly[ADP-ribose] polymerase, CD38), transport (connexin 43), and biosynthesis (NAMPT, NMNATs). Unsupervised clustering analysis identified a group of RA patients with the highest inflammatory profile, the lowest NAD+ levels, and the highest disease activity (as shown by the Disease Activity Score in 28 joints). NAD+ levels were modulated by anti-TNF therapy in parallel with the clinical response. In vitro studies using PBMCs from RA patients showed that nicotinamide riboside and nicotinamide increased NAD+ levels via NAMPT and NMNAT and reduced their prooxidative, proapoptotic, and proinflammatory status. CONCLUSION: RA patients display altered NAD+ metabolism, directly linked to their inflammatory and disease activity status, which was reverted by anti-TNF therapy. The preclinical beneficial effects of NAD+ boosters, as shown in leukocytes from RA patients, along with their proven clinical safety, might pave the way for the development of clinical trials using these compounds.