Metabolic syndrome

Metabolic syndrome is not a single condition but rather a cluster of risk factors that when present at same time, they significantly increase the risk of type 2 diabetes, heart attacks and strokes (1).  It is diagnosed when three or more of these risk factors are present in an individual: abdominal obesity, insulin resistance, hypertension and dyslipidaemia (high triglycerides and/or low HDL cholesterol) (2). Metabolic syndrome is preventable and reversible, and its primary treatment focuses on intensive lifestyle changes (3).

In the UK, approximately one in four adults meets the criteria for metabolic syndrome, making it a highly prevalent condition (4). Though often asymptomatic in early stages, metabolic syndrome reflects underlying metabolic dysfunction that, if unaddressed, can progress to chronic diseases with high morbidity and mortality (5,6).

Metabolic syndrome contributes to cardiovascular disease through cardiometabolic dysfunction, such as inflammation, oxidative stress, endothelial dysfunction and atherosclerosis (6,7). Cardiovascular disease represents the second cause of death in the UK, accounting for around 170,000 deaths each year, roughly one in four deaths nationally (8).

Metabolic syndrome is on the rise, and it is driven by sedentary lifestyles, highly processed diets, aging populations and environmental stressors (9).

Metabolic syndrome’s pathophysiology is complex, as genetics, diet and lifestyle factors all interact to drive metabolic dysfunction (1,10). Insulin resistance and chronic low-grade inflammation are at the core metabolic syndrome (10). However, the exact mechanisms behind it are not completely understood. Some researchers emphasise insulin resistance as the main and primary causal factor, and others suggest oxidative stress, inflammation and mitochondrial dysfunction as the key drivers (10,11).

Insulin resistance and high glucose levels

Insulin resistance is a state in which the normal ability of insulin to promote glucose uptake into peripheral tissues is impaired. This means that muscles, the liver and adipose tissue respond less effectively to insulin. To compensate, the pancreas produces more insulin, leading initially to hyperinsulinemia and high glucose levels. Both insulin and glucose are pro-inflammatory. Sustained high levels of insulin and glucose in the blood, eventually lead to type 2 diabetes (12).

Adipose tissue dysfunction

Excess visceral fat, particularly around the abdomen, secretes inflammatory adipokines/cytokines and free fatty acids that exacerbate insulin resistance and promote chronic low-grade inflammation (13).

Dyslipidaemia

Elevated triglycerides and low HDL (good) cholesterol arise from disturbed lipid metabolism associated with insulin resistance. These lipid abnormalities promote inflammation of the arteries which lead to atherosclerosis (14). 

Hypertension

Altered insulin signalling affects blood vessel function and sodium retention, contributing to elevated blood pressure (15). Under normal conditions, insulin promotes vasodilation by stimulating nitric oxide production in the inside of vessels (endothelium). However, when there is insulin resistance, nitric oxide production is impaired, blood vessels lose their ability to dilate effectively, and vascular stiffness increases (15).

Chronic inflammation and oxidative stress

Persistent low-grade inflammation is a key pathogenic component, linking metabolic syndrome with endothelial dysfunction and cardiovascular disease. Oxidative stress reduces nitric oxide availability, making vessels tighter, it damages endothelial cells, and promotes vascular inflammation. All of this contributes to arterial damage and atherosclerosis (11). 

As the underlying mechanisms of metabolic syndrome are complex and multifactorial, treatment needs to be holistic and multidimensional, an approach to which herbal medicine is particularly well suited.

Metabolic syndrome arises from the interaction of genetic susceptibility and lifestyle factors. Ethnicity, family history, and inherited genetic variation significantly shape an individual’s risk. For example, studies show that variants in the APOC3 gene, which encodes apolipoprotein C3, a component of triglyceride-rich lipoproteins, such as very low-density lipoproteins (VLDL), have been associated with elevated triglycerides and increased likelihood of developing metabolic syndrome (16).

However, genetic predisposition alone is rarely sufficient. Environmental triggers and lifestyle factors strongly influence whether this susceptibility is expressed. Central or visceral adiposity is one of the most influential causes. Visceral fat is metabolically active and releases adipokines and inflammatory mediators that promote insulin resistance, endothelial dysfunction, and dyslipidaemia (17).

Physical inactivity also reduces insulin sensitivity and contributes to weight gain and adverse lipid profiles. Diet plays a role in the development of some of the risk factors that constitute metabolic syndrome (17).  A diet high in refined carbohydrates and added sugars increase the likelihood of developing insulin resistance and visceral fat. A diet high in saturated fats also increased the chances of developing visceral fat as well as dyslipidaemia, contributing to high triglycerides and high LDL (bad) cholesterol (18). Excess salt and sodium is linked to hypertension which is another key component of metabolic syndrome (15).

Chronic psychological stress and inadequate or disrupted sleep alter cortisol regulation, appetite signalling, and insulin pathways, contributing to the mechanisms of metabolic dysfunction and endothelial inflammation (19). Persistent systemic inflammation, as seen in long-standing conditions, such as HIV, Chagas disease and autoimmune disorders, are associated with increased chances of developing metabolic syndrome (20,21,22). 

Advancing age is another risk factor that increases the susceptibility of developing it, as metabolic flexibility declines and insulin resistance becomes more common (23).

Metabolic syndrome is often a silent condition as many people with it are asymptomatic. Metabolic syndrome is identified by a cluster of measurable cardiometabolic risk factors rather than by a distinct set of symptoms (24).

Primary clinical signs for its diagnosis

• Abdominal adiposity: Increased waist circumference, men > 94 cm (> 37 inches), women > 80 cm (> 32 inches) (24). For South Asian and Chinese men >= 90 cm and women >= 80 cm. This often the most visible clinical sign (25). 
• Raised blood pressure:  blood pressure above ≥130/85 mmHg, or current treatment for hypertension (2,23).
• Elevated fasting plasma glucose: fasting glucose ≥5.6 mmol/L, or established type 2 diabetes (2,23).
• Elevated triglycerides: ≥1.7 mmol/L, or treatment for raised triglycerides (2,23).
• Reduced HDL cholesterol: <1.0 mmol/L in men, <1.3 mmol/L in women (2,23).

Symptoms 

• Tiredness 
• Reduced exercise tolerance
• Brain fog or difficulty concentrating
• Increased thirst or increased urination if persistent high glucose levels
• Headaches, if high blood pressure present
• Visible central weight gain (26)

The herbal approach should be comprehensive to address all aspects of metabolic syndrome. Herbalists focus on reducing abdominal fat tissue, improving blood pressure, improving the lipid profile by reducing triglycerides and increasing HDL, and improving insulin resistance (27).

Reducing abdominal and visceral adiposity is central to improving the overall metabolic picture. Coleus (Coleus forskohlii) is traditionally used to support weight and fat loss, with actions linked to modulation of cyclic AMP and lipolysis (27). Liquorice (Glycyrrhiza glabra) can also play a supportive role in body fat reduction, though caution is required with long term use in individuals with hypertension (28).

The constituent berberine from Berberis species has strong clinical support for metabolic syndrome. A recent systematic review and meta-analysis of randomized placebo-controlled trials concluded that berberine improves components of metabolic syndrome, including glucose metabolism, triglycerides, lipid profiles and waist circumference, while improving insulin signalling and reducing inflammation (29). Berberine has also been shown to have antihypertensive properties and endothelial protection, being able to relax blood vessels (30). Examples of berberine containing plants include barberry (Berberis vulgaris) and Oregon grape (Mahonia aquifolium).  

Improving insulin sensitivity and glycaemic control is another fundamental aspect of the treatment strategy. Gymnema (Gymnema sylvestre) is particularly suited where sugar cravings and diabetes are present, helping to regulate glucose metabolism and reduce sweet taste perception (27,31,32). Goat’s rue (Galega officinalis), the plant from which metformin was synthesised, can also be used alongside gymnema as it has glucose lowering actions and it lowers insulin resistance (33). Fenugreek (Trigonella foenum-graecum) and ginseng (Panax ginseng) offer additional support for glycaemic control and insulin sensitivity (33,34).

Berberine again has a central role here due to its insulin-sensitising and anti-inflammatory effects (35,36). Curcumin from turmeric (Curcuma longa) is supported by randomized clinical evidence and systematic reviews showing improvements in insulin sensitivity and dyslipidaemia particularly in metabolic syndrome (37,38). Its ability to modulate inflammatory cytokines and improve endothelial function is especially relevant given the inflammatory component of insulin resistance and metabolic syndrome.

Hepatic support is often required, especially where fatty liver or elevated gamma-glutamyl transferase (GGT) are present. Milk thistle (Silybum marianum) has hepatoprotective properties, which makes it beneficial in cases of non-alcoholic fatty liver disease and raised liver enzymes, particularly when these coexist with metabolic syndrome (27).

A meta-analysis showed that milk thistle supplementation can reduce total cholesterol and LDL, reduce triglycerides and improve glucose metabolism (39). In a clinical trial in people with type 2 diabetes, silymarin at 140 mg three times daily for 45 days reduced triglycerides and LDL, increased HDL, lowered total cholesterol and decreased fasting blood glucose levels and serum insulin (40).

Addressing the lipid profile directly, by reducing triglycerides and increasing HDL, can also be supported with garlic (Allium sativum) and artichoke (Cynara scolymus) (27,41,42). Garlic has demonstrated lipid-lowering and modest antihypertensive effects in clinical studies, likely mediated through nitric oxide modulation and antioxidant activity (41,43). Both artichoke and chicory extracts have been associated with improved cholesterol and triglyceride parameters, alongside digestive support that may further benefit metabolic regulation (42).

Green tea (Camellia sinensis) can lower total cholesterol and LDL (44). Green tea contributes cardiometabolic support through antioxidant and metabolic effects. These herbs, together with Berberis species can contribute to an improvement of triglycerides and HDL balance.

Where hypertension is present, hawthorn (Crataegus spp.), yarrow (Achillea millefolium) and limeflower (Tilia spp.) can be considered to support vascular tone (27). These all have a vasodilatory effect, helping bring down blood pressure. They work best in combination. The use of hawthorn has been supported by clinical evidence. A recent meta-analysis showed that hawthorn significantly reduces blood pressure.

Hawthorn contains flavonoids that improve vascular endothelial function, reduce inflammation, and increase nitric oxide-mediated vasodilation (45). Garlic again can offer an additional benefit through modest blood pressure reduction. 

Given the strong link between chronic stress, cortisol dysregulation and central fat deposition, stress management is important. The use of nervines can be relevant depending on the individual presentation. 

Clinical trials consistently show that weight reduction through dietary change and physical activity significantly improves all core components of metabolic syndrome — waist circumference, blood pressure, fasting glucose and lipid profile (18, 46). A Mediterranean diet containing vegetables, legumes, whole grains, good-quality olive oil, nuts and seeds has strong evidence improving insulin sensitivity and lowering inflammation (46). A calorie restricted low glycaemic load (GL) diet with good fibres has also been proposed as beneficial to improve insulin sensitivity, glucose levels and decrease abdominal fat (27).

Regular movement is just as important (17). Regular moderate-to-vigorous exercise improves insulin sensitivity independent of weight loss and reduces visceral adiposity. This could be brisk walking, cycling, swimming or strength training, for example (17).

Stress and sleep are often underestimated drivers of metabolic imbalance. Ongoing stress and poor-quality sleep disrupt cortisol cycles, appetite regulation and glucose control, making it harder for the body to maintain metabolic stability (19). Therefore, stress reduction activities and optimal sleep hygiene are equally fundamental.

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