HIF isoforms in the skin differentially regulate systemic arterial pressure

Human high-altitude adaptation: forward genetics meets the HIF pathway

Humans have adapted to the chronic hypoxia of high altitude in several locations, and recent genome-wide studies have indicated a genetic basis. In some populations, genetic signatures have been identified in the hypoxia-inducible factor (HIF) pathway, which orchestrates the transcriptional response to hypoxia. In Tibetans, they have been found in the HIF2A (EPAS1) gene, which encodes for HIF-2α, and the prolyl hydroxylase domain protein 2 (PHD2, also known as EGLN1) gene, which encodes for one of its key regulators, PHD2. High-altitude adaptation may be due to multiple genes that act in concert with one another. Unraveling their mechanism of action can offer new therapeutic approaches toward treating common human diseases characterized by chronic hypoxia.

Regulation of obesity and insulin resistance by hypoxia-inducible factors

In obesity, dysregulated metabolism and aberrant expansion of adipose tissue lead to the development of tissue hypoxia that plays an important role in contributing to obesity-associated metabolic disorders. Recent studies utilizing adipocyte-specific hypoxia-inducible factor-α (HIF-α) gain- or loss-of-function animal models highlight the pivotal involvement of hypoxic responses in the pathogenesis of obesity-associated inflammation and insulin resistance. HIF-1α, a master transcription factor of oxygen homeostasis, induces inflammation and insulin resistance in obesity, whereas its isoform, HIF-2α, exerts opposing functions in these obesity-associated metabolic phenotypes. In this review, recent evidence elucidating functional implications of adipocyte HIFs in obesity and, more importantly, how these regulate obesity-associated inflammation, fibrosis, and insulin resistance will be discussed. Further, we propose that modulation of HIF-1 could be a potential novel therapeutic strategy for antidiabetic treatment.

Unsuspected task for an old team: succinate, fumarate and other Krebs cycle acids in metabolic remodeling

Seventy years from the formalization of the Krebs cycle as the central metabolic turntable sustaining the cell respiratory process, key functions of several of its intermediates, especially succinate and fumarate, have been recently uncovered. The presumably immutable organization of the cycle has been challenged by a number of observations, and the variable subcellular location of a number of its constitutive protein components is now well recognized, although yet unexplained. Nonetheless, the most striking observations have been made in the recent period while investigating human diseases, especially a set of specific cancers, revealing the crucial role of Krebs cycle intermediates as factors affecting genes methylation and thus cell remodeling. We review here the recent advances and persisting incognita about the role of Krebs cycle acids in diverse aspects of cellular life and human pathology.