Functional Changes in Metabolic Syndrome
Authors: Esra Bihter Gürler  , Hülya Çevik ARAS  , Nagihan Bostanci  
Published: January 2025

Metabolic Syndrome (MetS) is a condition characterized by the cooccurrence of several cardiovascular risk factors, including insulin resistance, obesity,
dyslipidemia, and hypertension. The development of MetS is closely linked to visceral
adiposity, which refers to fat accumulation around critical vital organs in the abdominal
cavity. Visceral fat is metabolically active and produces adipokines, proteins that
regulate energy balance and play a role in inflammation and atherosclerosis. Some
adipokines, such as leptin and adiponectin, have beneficial effects on glucose
homeostasis and are considered protective against MetS. However, other adipokines,
such as visfatin and resistin, contribute to glucose intolerance and have pro-atherogenic
properties. Visceral obesity also contributes to the development of MetS through its
effects on blood pressure. It activates the sympathetic nervous system, the reninangiotensin-aldosterone system, and insulin resistance, leading to elevated blood
pressure.
Another critical factor in the development of MetS is the activation of the lectin-like
oxidized low-density lipoprotein receptor-1 (LOX-1). LOX-1 is a protein that acts as a
receptor for oxidized LDL on the cell surface. Its activation leads to the production of
reactive oxygen species, a decrease in nitric oxide, and increased expression of
molecules contributing to hypertension and vascular damage. LOX-1 is also involved
in the development of other complications associated with MetS, such as nephropathy
and left ventricular hypertrophy.The renin-angiotensin-aldosterone system (RAAS) regulates blood volume, electrolyte
balance, and vascular resistance. In patients with MetS, the activation of RAAS leads
to increased levels of angiotensin II (Ang II) and aldosterone, which have various
effects on blood pressure and sodium and water retention. Ang II also contributes to
oxidative stress and inflammation in the vasculature.
Insulin resistance, a key feature of MetS, disrupts the insulin signaling process in
adipose tissue, leading to increased lipolysis and elevated levels of circulating free fatty
acids. These fatty acids further worsen insulin resistance and contribute to impaired
glucose metabolism.Oxidative stress, characterized by an imbalance between the production of reactive
oxygen species and the body's antioxidant defenses, is closely associated with the
development of MetS. Hyperlipidemia and hyperglycemia, standard features of MetS,
are linked to increased oxidative stress and ROS production. Oxidative stress and the
activation of RAAS and LOX-1 contribute to the progression of dyslipidemia, type 2
diabetes, hypertension, and cardiovascular diseases.
The oral-gut-liver axis is an emerging concept that suggests a relationship between oral
infections, such as periodontitis, and metabolic dysfunction, including MetS and liver
diseases. Periodontitis has been associated with chronic liver diseases, such as nonalcoholic fatty liver disease (NAFLD) and liver cirrhosis. The translocation of oral
bacteria from the mouth to the gut may contribute to gut dysbiosis, increased intestinal
permeability, and systemic inflammation, which can worsen liver functions.
Overall, the development of MetS involves the interplay of various factors, including
visceral obesity, adipokines, LOX-1 activation, insulin resistance, oxidative stress, and
the oral-gut-liver axis. Understanding these mechanisms is crucial for preventing and
managing MetS and its associated complications. Further research is needed to fully
elucidate the roles of individual factors and develop targeted interventions for MetS.