Lipids are a large and diverse class of biomolecules that exert multiple biochemical functions, such as fueling energy production, and building blocks for plasma membrane and chemical signals during cellular communication. Lipids have been found especially important in such tissues as the adipose tissue, liver and intestine for energy storage or lipid turnover [1], while accreted in the skeletal muscle, mammary glands, macrophages and adrenal cortex [2]. Under energy-rich conditions, lipids synthesis is highly conservative; under energy-poor conditions, lipids accumulation enables organisms to survive, and stored lipids are then utilized in need of energy production. As evidenced, abnormal lipid metabolism is associated with type 2 diabetes mellitus, obstructive sleep apnea, coronary artery disease, nonalcoholic fatty liver diseases, cancer, etc. [3, 4]. Much research has been conducted to reveal the essential roles of lipid metabolism in energy homeostasis and metabolic diseases. The discovery of diverse characteristics of lipids may shed light on new therapeutic strategies for metabolic diseases.

Adipose tissues are traditionally considered as the major sites for storage of excess lipids. As endocrine organs, dysfunctional adipose tissues will lead to the variation of adipokines secretion. Adipose tissues consist of two functionally distinct types of adipose tissues: white adipose tissues and brown adipose tissues. The former store excess calories in the form of triglycerides and release them in need; the latter dissipate stored chemical energy as heat during nonshivering thermogenesis. In this special topic, Li and Li [5] summarize the current knowledge about leptin, one of the most important adipokines, in the hope of seeking new weapons for the battle against obesity. Yuan et al. [6] review some thermodynamic and cellular advances in brown fat research and discuss the potential of brown fat in treating obesity and metabolic diseases. Insulin resistance is a complicated metabolic disorder closely linked to ectopic lipid accumulation as well as activation of unfolded protein response pathways and innate immune pathways. The review article by Chen [7] comprehensively portrays the roles of adapter proteins in insulin resistance and lipid homeostasis. The paper by Zhou et al. [8] describes that adaptor protein APPL1 can be phosphorylated at Ser636 upon epidermal growth factor (EGF) stimulation, which consequently facilitates the interaction with epidermal growth factor receptor (EGFR) and sensitizes EGFR signaling. Besides altered glucose metabolism, lipid metabolism has also been demonstrated to play a key role in cancer cell survival and proliferation under stressful hypoxic conditions. Chen and Li [9] briefly review the aberrant lipid metabolism in cancer development with a special focus on fatty acid uptake and de novo synthesis, storage and degradation. Finally, an research article by Liu et al. [10] introduces a reciprocal inhibitory relationship between adiponectin and cytosolic thioredoxin in patients with acute exacerbations of chronic obstructive pulmonary disease.

We anticipate that this special topic will attract broad attention to lipid metabolism and metabolic diseases and push forward relevant research.