Lipolysis is the metabolic pathway through which lipid triglycerides are hydrolyzed into a glycerol and free fatty acids. It is used to mobilize stored energy during fasting or exercise, and usually occurs in fat adipocytes. The most important regulatory hormone in lipolysis is insulin; lipolysis can only occur when insulin action falls to low levels, as occurs during fasting. Other hormones that affect lipolysis include leptin, glucagon, epinephrine, norepinephrine, growth hormone, atrial natriuretic peptide, brain natriuretic peptide, and cortisol.
Brown adipose tissue (BAT) or brown fat makes up the adipose organ together with white adipose tissue. Brown adipose tissue is found in almost all mammals.
Adipose tissue is a loose connective tissue composed mostly of adipocytes. It also contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, vascular endothelial cells and a variety of immune cells such as adipose tissue macrophages. Its main role is to store energy in the form of lipids, although it also cushions and insulates the body.
Adipocytes, also known as lipocytes and fat cells, are the cells that primarily compose adipose tissue, specialized in storing energy as fat. Adipocytes are derived from mesenchymal stem cells which give rise to adipocytes through adipogenesis. In cell culture, adipocyte progenitors can also form osteoblasts, myocytes and other cell types.
Panniculitis is a group of diseases whose hallmark is inflammation of subcutaneous adipose tissue. Symptoms include tender skin nodules, and systemic signs such as weight loss and fatigue.
A skin condition, also known as cutaneous condition, is any medical condition that affects the integumentary system—the organ system that encloses the body and includes skin, nails, and related muscle and glands. The major function of this system is as a barrier against the external environment.
Erythema toxicum neonatorum is a common, non-threatening rash in newborns. It appears in 4-70% of newborns within the first week of life, and it typically improves within 1–2 weeks. It only occurs during the newborn period, but may appear slightly later in premature babies. The rash has a variable appearance. It typically includes blotchy red spots, often with overlying firm, yellow-white bumps or pus-filled boils. There may be only a few or many lesions. The lesions can appear almost anywhere on the body, and individual lesions may appear and disappear within hours. There are no other symptoms associated with erythema toxicum neonatorum, and the rash does not have any long-term effects on the skin. Erythema toxicum neonatorum is not harmful and does not require any treatment.
Subcutaneous fat necrosis of the newborn is a rare form of lobular panniculitis occurring in newborns that is usually self-remitting and non-recurring. Proposed causes include perinatal stress, local trauma, hypoxia and hypothermia, though the exact cause is unknown. It has been suggested that the brown fat seen in newborns is more sensitive to hypoxic injury than fat seen in adults, and that such hypoxia, usually in the context of a complicated birth, leads to the fat necrosis. Complications can include hypercalcemia, hyperlipidemia, dehydration, hypoglycemia, seizures, vomiting, constipation, and thrombocytopenia, and can present months after the onset of SCFN symptoms.
White adipose tissue or white fat is one of the two types of adipose tissue found in mammals. The other kind is brown adipose tissue. White adipose tissue is composed of monolocular adipocytes.
Fat necrosis is a form of necrosis that is caused by the action of lipases on adipocytes.
Neonatal acne, also known as acne neonatorum, is an acneiform eruption that occurs in newborns or infants within the first 4-6 weeks of life, and presents with open and closed comedones on the cheeks, chin and forehead.
Lupus erythematosus panniculitis presents with subcutaneous nodules that are commonly firm, sharply defined and nontender.
Transient neonatal pustular melanosis (TNPM), also known as pustular melanosis, is a type of neonatal pustular eruption that is a transient rash common in newborns. It is vesiculopustular rash made up of 1–3 mm fluid-filled lesions that rupture, leaving behind a collarette of scale and a brown macule. The lesions are fragile and with no surrounding erythema. This rash occurs only in the newborn stage, usually appearing a few days after birth, but pigmented macules are sometimes already present at birth. The rash usually fades over three to four weeks but may linger for up to three months after birth. It can occur anywhere on the body, including the palms and soles.
Septal panniculitis is a condition of the subcutaneous fat affecting the layer of adipose tissue that lies between the dermis and underlying fascia, of which there are two forms: acute erythema nodosum and chronic erythema nodosum.
Congenital generalized lipodystrophy is an extremely rare autosomal recessive condition, characterized by an extreme scarcity of fat in the subcutaneous tissues. It is a type of lipodystrophy disorder where the magnitude of fat loss determines the severity of metabolic complications. Only 250 cases of the condition have been reported, and it is estimated that it occurs in 1 in 10 million people worldwide.
Acquired generalized lipodystrophy (AGL), also known as Lawrence syndrome and Lawrence–Seip syndrome, is a rare skin condition that appears during childhood or adolescence, characterized by fat loss affecting large areas of the body, particularly the face, arms, and legs. There are four types of lipodystrophy based on its onset and areas affected: acquired or inherited, and generalized or partial. Both acquired or inherited lipodystrophy present as loss of adipose tissues, in the absence of nutritional deprivation. The near-total loss of subcutaneous adipose tissue is termed generalized lipodystrophy while the selective loss of adipose tissues is denoted as partial lipodystrophy. Thus, as the name suggests, AGL is a near-total deficiency of adipose tissues in the body that is developed later in life. It is an extremely rare disease with only about 100 cases reported worldwide. There are three main etiologies of AGL suspected: autoimmune, panniculitis-associated, or idiopathic. After its onset, the disease progresses over a few days, weeks, months, or even in years. Clinical presentations of AGL are similar to other lipodystrophies, including metabolic complications and hypoleptinemia. Treatments are also similar and mainly supportive for symptomatic alleviation. Although HIV- or drug-induced lipodystrophy are types of acquired lipodystrophy, their origins are very specific and distinct and hence are usually not discussed with AGL.
HIV-associated lipodystrophy is a condition characterized by loss of subcutaneous fat associated with infection with HIV.
Livedoid vasculopathy(LV) is an uncommon thrombotic dermal vasculopathy that is characterized by excruciating, recurrent ulcers on the lower limbs. Livedo racemosa, a painful ulceration in the distal regions of the lower extremities, is the characteristic clinical appearance. It heals to form porcelain-white, atrophic scars, also known as Atrophie blanche.
Weber–Christian disease is a cutaneous condition characterized by recurrent subcutaneous nodules that heal with depression of the overlying skin.
Fat removal procedures are used mostly in cosmetic surgery with the intention of removing unwanted adipose tissue. The procedure may be invasive, as with liposuction, or noninvasive using laser therapy, radiofrequency, ultrasound or cold to reduce fat, sometimes in combination with injections.
