Fat is Fat
Being overweight can really slow you down. Your love handles are more apparent these days. It gets on your nerves when your doctor constantly emphasizes the need to lose weight. He or she provides a list of possible side effects associated with the extra chichos. Diabetes type-2, hypertension, stroke, gallbladder disease, high LDL cholesterol, coronary disease, etc., fall into this category. Failure to take corrective action at the right time can result in death. It's helpful for human health to have adipose tissue, but too much or too little can be problematic. Fat is common in the general population.
In general, it has been accepted that adipose tissue is a biologically active organ. Through research, adipose tissue has been discovered to possess other properties, besides storing energy in the form of lipids and insulating other organs. One of its functions is to manufacture and release adipokines, which are hormones specific to adipose tissue. The endocrine activity of fat tissue is controlled by a variety of genetic, lipid, and protein compounds. Together with the liver and skeletal muscle, it maintains glucose metabolism. A person's metabolic health may suffer when one of the three main functions of adipose tissue, which are lipid storage, endocrine function, and insulin responsiveness, is impaired. As mentioned above, too much adipose tissue is a major risk factor for multiple diseases.
By now, you can conclude that excessive lipid accumulation leads to obesity, since adipose tissue is the main organ for storing fat. Hyperplasia and hypertrophy are two terms to keep in mind when thinking about adipose growth. Basically, hyperplasia is the ability to create new adipocytes (fat cells) from existing adipocytes (e.g. carrying excess weight) by a highly complex biochemical process known as adipogenesis. In contrast, hypertrophy relies on dietary fats circulating in the bloodstream or a series of biochemical reactions known as the fatty acid synthesis pathway. This type of reaction can be triggered by high-fat diets. Balance between hyperplasia and hypertrophy is one parameter that contributes to healthy adipose tissue expansion and metabolic health.
Chronic low-grade inflammation is another area of concern. An injury is an example of inflammation, which is a normal and necessary physiological reaction. However, when it becomes chronic, it increases the risk of obesity and other diseases. Over time, this response system produces pro-inflammatory compounds that tax the immune system. Tumor necrosis factor alpha (TNFa) is a pro-inflammatory compound that promotes insulin resistance in adipocytes by inhibiting insulin receptor activity and insulin-sensitive glucose transport. As a consequence of excess insulin and fatty acids wandering the bloodstream, macrophages, a type of immune cell, are recruited to the adipose tissue. They then trigger the production of immune-stimulating substances like cytokines. Left unresolved, the situation eventually turns into a sick cycle.
The function of adipocytes and their structural position are determined by the type of adipocyte present in the tissue. Adipocytes differ according to their biochemical profiles. Adipose tissue can be classified into the following types:
White adipose tissue (WAT) – the main site of energy storage in the form of lipid
Brown and beige fat (BAT)– provide a source of energy expenditure due to their heat-generating characteristics
Essentially, brown adipose tissue promotes weight loss, while white adipose tissue stores lipids in anticipation of a shortage of energy. Subcutaneous adipose tissue, which is beneath the skin, is generally considered healthy. A healthy example of good WAT is fat around the buttock region. As for visceral adipose tissue, it is located around internal organs and correlates with inflammation and increases the likelihood of developing metabolic disease. Fat inside the belly is an example.
Adipose tissue contributes to endocrine regulation through the release of compounds that affect glucose levels. They are collectively referred to as adipokines. The three adipokines you should pay close attention to are leptin, resistin and adiponectin.
Leptin – under normal conditions it is typically present in high amounts and tells the brain to stop eating. It is therefore labelled an appetite suppressant. Obesity is caused by the absence or mutation of this hormone. It's interesting to know that leptin is a proinflammatory adipokine. Excessive adipokines can have health repercussions, but it also helps you lose weight
Resistin – as its name suggests, resistin promotes inflammation and insulin resistance. Macrophages produce this hormone
Adiponectin – an anti-inflammatory adipokine that is involved in enhancing insulin activity in a number of tissues. Most of its anti-diabetic effects are attributed to its ability to suppress liver glucose production. It is through adiponectin-specific receptors that muscle cells, liver cells, and the heart receive more glucose. Blood adiponectin levels tend to be low in obese and T2DM individuals.
Overall, obesity disrupts lipid storage, resulting in insulin resistance and disrupting the normal functions of adipocytes. In turn, insulin resistance disrupts adipocyte signaling and metabolism, which leads to increased fat breakdown. Lipids roaming in the bloodstream for an extended period of time can cause inappropriate lipid storage and insulin resistance in other tissues such as the liver and skeletal muscles. In summary, leptin and resistin are produced and released by healthy adipocytes. A person's overall health benefits from their insulin sensitivity and lower fat oxidation. In contrast, compromised adipocytes are predominantly deposited in the visceral space and are associated with more proinflammatory macrophages. The blood also circulates more leptin and resistin. These factors make it easier for fatty acids to travel through the bloodstream. Probably by now you know what I'm about to stress, the need to have a balanced life. Until next time, Stay Strong & Stay Vivid!
Reference
Harvey, I. et al. (2020). Adipose Tissue in health and disease. The Royal Society Publishing. https://doi.org/10.1098/rsob.200291.
Brandão, B.B., Poojari, A. & Rabiee, A. (2021). Thermogenic Fat: Development, Physiological Function, and Therapeutic Potential. https://doi.org/10.3390/ijms22115906.
