Mesenteric fat is a type of fat located within the abdomen, residing within the mesentery. The mesentery is a continuous fold of tissue that anchors the intestines to the back wall of the abdomen, providing structural support. This fat plays a role in overall bodily functions beyond simple energy storage. Its unique location and characteristics contribute to its involvement in various physiological processes and can influence health conditions when dysfunctional.
Where Mesenteric Fat Resides and How It Differs
Mesenteric fat is situated within the mesentery, a double layer of peritoneum—the membrane lining the abdominal cavity. This tissue structure attaches the small and large intestines to the posterior abdominal wall, holding them in place while allowing for movement during digestion. The mesentery also provides a pathway for blood vessels, lymphatic vessels, and nerves to reach and supply the intestines.
This type of fat differs from other fat depots in the body. Subcutaneous fat, for example, is found directly under the skin, often visible and pinchable, and is distributed across areas like the hips, thighs, buttocks, and abdomen. In contrast, mesenteric fat is a form of visceral fat, stored deep within the abdominal cavity, surrounding internal organs such as the liver, pancreas, and intestines. Unlike subcutaneous fat, visceral fat is not visible from the outside and lies beneath the abdominal muscles.
Mesenteric fat’s unique anatomical position and metabolic activity distinguish it from other fat types. It is directly connected to the intestines, forming a continuous structure along most of the small and large bowel. This proximity to the gut influences its metabolic and inflammatory properties. Mesenteric fat is more metabolically active, cellular, vascular, and innervated than subcutaneous fat, and it contains a greater number of inflammatory and immune cells. It also exhibits higher sensitivity to lipolysis and is more insulin-resistant compared to subcutaneous fat.
The Active Roles of Mesenteric Fat
Beyond simply storing energy, mesenteric fat actively participates in various bodily functions, acting as a dynamic organ. It is involved in complex metabolic and endocrine processes, and plays a role in the immune system, influencing local inflammatory responses.
It secretes various hormones, known as adipokines, and inflammatory molecules. These adipokines, such as leptin, resistin, and chemerin, modulate metabolic functions and exert regulatory roles within the immune system. Mesenteric adipocytes can also produce C-reactive protein (CRP), an inflammatory marker, especially when triggered by local inflammation and bacterial presence.
This fat tissue is involved in the immune system, particularly through its interaction with the gut microbiome and its role in local inflammatory responses. Mesenteric fat contains fat cells, immune cells like macrophages, T cells, and B cells, and non-immune cells such as endothelial cells and fibroblasts. These cells become activated and contribute to inflammation and immunity. For instance, bacterial translocation from the intestine into the mesenteric fat can activate adipocytes and immune cells, influencing the local immune response.
Mesenteric Fat’s Link to Health Conditions
Dysfunctional or excessive mesenteric fat can contribute to various health issues. Its accumulation is associated with an increased risk of metabolic syndrome, a cluster of conditions including high blood pressure, high blood sugar, excess waist fat, and abnormal cholesterol or triglyceride levels. Mesenteric fat thickness has been identified as an independent factor for metabolic syndrome, with a thickness of 10 mm or more potentially indicating an increased risk. This heightened metabolic activity can lead to increased free fatty acid release, which may contribute to insulin resistance and affect systemic lipid metabolism, increasing the risk for cardiovascular disease.
Mesenteric fat plays a role in inflammatory bowel diseases (IBD), particularly Crohn’s disease. In Crohn’s disease, mesenteric fat can become enlarged and inflamed, a condition often referred to as “creeping fat.” This creeping fat wraps around the circumference of the inflamed intestine, sometimes covering more than 50% of the bowel. It contains activated cells, making it an active participant in the inflammatory processes seen in Crohn’s disease.
The presence of creeping fat is associated with complications in Crohn’s disease, such as thickened intestinal muscle walls, strictures (narrowing of the intestine that can cause blockages), and fibrosis or scarring. While its exact role in Crohn’s disease progression is still being investigated, it is thought to contribute to intestinal inflammation and fibrogenesis. Mesenteric fat’s inflammatory activity, including the production of pro-inflammatory cytokines like IL-6, has also been linked to conditions such as type 2 diabetes.