Around the world, about 4 in 10 adults have abnormal blood fat levels-known as dyslipidaemia-which raises their chances of getting heart disease. Many people with this condition are prescribed statins, medications that help lower the "bad" Low-density lipoprotein cholesterol (LDL-C) in the blood and, in doing so, help prevent serious heart-related problems. While statins do lower these harmful cholesterol levels, recent research suggests that statins might interfere with some of the positive effects that exercise typically has on muscle cells' energy centers (the mitochondria) and on a person's aerobic capacity. It is not yet fully understood how statins might influence these exercise benefits at the molecular level. To address this gap, the present study will look closely at how taking statins combined with a structured exercise program affects both the muscle cells and the whole-body fitness of people with dyslipidaemia. By using a wide-ranging protein analysis, the research aims to identify changes in muscle proteins and other metabolism-related factors that could explain why statins might alter the expected improvements from exercise.

Methods and Analysis In this 12-week study, we aim to enrol between 100 and 125 adults (aged 40-65 years, with dyslipidaemia without established heart disease); the trial is powered for the first 100, and recruitment will stay open up to 125 to offset potential drop-outs. Participants will be randomly split into one of four groups: (1) exercise plus a placebo (an inactive pill), (2) exercise plus a daily high-dose statin (atorvastatin, 80 mg), (3) a daily high-dose statin without exercise, or (4) a placebo without exercise. More participants will be placed in the exercise groups to better understand the combined effects of exercise and statins. The main measurement will be how well the muscle's mitochondria work, assessed by changes in an enzyme called citrate synthase (CS) from before the program to after. Other important measures will include overall fitness (using a peak oxygen uptake (VO2peak) test) and detailed protein analyses. The study will also look at genetic variations to see if they influence how each participant responds to the treatment.

Ethics and Sharing of Results The study has received approval from the Faroe Islands Ethical Committee (2024-10) and follows international guidelines to protect participants' rights and data. Once the research is complete, the findings will be shared in leading scientific journals for the broader public and medical community to learn from.

Dyslipidaemia, defined by abnormal lipid profiles (including raised total cholesterol, LDL-C, and triglycerides, as well as reduced high-density lipoprotein cholesterol (HDL-C), affects close to 40% of adults aged 25 years and above worldwide. This condition significantly contributes to global morbidity and mortality. In particular, excess LDL-C has been associated with elevated atherosclerotic cardiovascular disease (ASCVD) risk due to its central role in cholesterol transport into the arterial wall, facilitating plaque formation and atherogenesis. The scale of the problem is illustrated by data indicating that high LDL-C levels were linked to approximately 4.40 million deaths and 98.62 million Disability-adjusted life years in 2019 alone. Notably, the highest regional prevalence of hypercholesterolaemia has been reported in Europe, where more than half of the adult population exhibits elevated plasma cholesterol concentrations. The reduction of circulating LDL-C, whether through pharmacological agents or lifestyle interventions, thus remains a key strategy in mitigating ASCVD risk.

Among available therapies, statins are a cornerstone of dyslipidaemia management due to their efficacy in lowering LDL-C and consequent reduction in cardiovascular event rates. For instance, decreasing LDL-C by 1 mmol/L through statin therapy is associated with up to a 20% reduction in both cardiovascular events and all-cause mortality. While pharmacotherapy is central to risk management, exercise training is also strongly recommended to improve lipid profiles and enhance cardiovascular health. Even relatively modest increases in cardiorespiratory fitness (CRF), on the order of approximately 1 metabolic equivalent (MET), translate into significant survival benefits of 10-25%. As cardiovascular diseases remain a leading global health concern, understanding how statins may interact with exercise-based interventions is essential for developing optimized treatment strategies for patients with dyslipidaemia.

Recent evidence suggests that the concurrent use of statins and structured exercise training does not always produce additive benefits, as initially presumed. In particular, some studies have reported that statin therapy may attenuate improvements in CRF and skeletal muscle mitochondrial function typically observed with endurance training. For example, administration of simvastatin at 40 mg/day hindered the usual exercise-induced increase in citrate synthase (CS) activity and aerobic capacity following 12 weeks of endurance exercise training in overweight adults. Similarly, high-dose atorvastatin (80 mg/day) has been shown to impair mitochondrial oxidative capacity in skeletal muscle, even in individuals free from overt cardiometabolic disease. These results are consistent with a growing body of work linking statin use to mitochondrial perturbations within skeletal muscle tissue. However, the precise biological mechanisms responsible for these observations remain poorly characterized. Modern omics approaches, such as untargeted proteomic profiling, may help elucidate how statins impact the network of mitochondrial proteins and metabolic pathways involved in exercise adaptation.

In addition to mitochondrial dysregulation, statin therapy-particularly at high doses-has been associated with a heightened risk of incident type 2 diabetes mellitus (T2DM). The underlying mechanisms appear multifactorial, involving alterations in insulin sensitivity and secretory function. Statins may diminish Glucose transporter type 4 (GLUT4)-mediated glucose uptake, affect mitochondrial energy transduction in skeletal muscle and adipose tissue, and promote lipotoxicity in pancreatic beta cells, collectively increasing insulin resistance and impairing normal insulin secretion. Thus, while statins robustly lower LDL-C and cardiovascular risk, their influence on glycemic control and metabolic health parameters warrants careful patient selection and ongoing glucose monitoring, especially in individuals predisposed to diabetes.

Musculoskeletal side effects, referred to as statin-associated muscle symptoms (SAMS), are another important consideration. Affecting an estimated 5-30% of statin users, SAMS range from mild myalgias to more significant muscle weakness, potentially prompting discontinuation of therapy and reducing adherence. This issue may also discourage regular physical activity and thereby negate some of the positive lifestyle modifications critical for long-term health management. Physical exertion may exacerbate these muscle symptoms, promoting a more sedentary pattern in individuals on statins. Although the pathophysiology of SAMS is not fully delineated, mitochondrial dysfunction related to impaired complexes III and IV activity, as well as reduced coenzyme Q10 availability, has been implicated.

Moreover, genetic polymorphisms can modulate statin pharmacodynamics and pharmacokinetics, potentially altering muscle tissue statin exposure and influencing inter-individual variability in both therapeutic and adverse responses to these agents. To date, however, the extent to which genetic variation might modify the interaction between statin therapy and exercise adaptations (on parameters such as mitochondrial function and systemic fitness) remains unknown.

In summary, although statins effectively diminish ASCVD risk by lowering LDL-C, emerging data suggest statins can reduce the beneficial effects of exercise training on skeletal muscle mitochondria and CRF. In addition, high-dose statin therapy may increase susceptibility to T2DM and aggravate muscle-related symptoms, thereby influencing the overall therapeutic benefit-risk profile. Despite considerable investigation in related areas, the precise molecular mechanisms underlying these effects, as well as the influence of genetics on this interplay, remain unclear. Notably, previous research has not yet encompassed a comprehensive, randomized, double-blinded, placebo-controlled trial that examines the simultaneous impact of statin therapy and structured exercise training on cardiovascular, muscular, and metabolic endpoints in dyslipidaemic individuals aged 40-65 years, including in-depth molecular phenotyping and genetic analyses.

Objective The present study aims to determine how statin therapy and exercise training, alone and in combination, influence whole-body aerobic capacity and mitochondrial function in individuals with dyslipidaemia but without established ASCVD. By employing untargeted proteomic methods, the investigation will identify molecular signatures and pathways through which statins may modify exercise-induced alterations in mitochondrial protein composition and metabolic phenotypes. An embedded sub-analysis will evaluate the role of genetic polymorphisms influencing statin pharmacodynamics and pharmacokinetics, thereby assessing how these genetic factors might shape individual variability in responses at both the muscle tissue and systemic levels. This integrative approach is expected to advance our understanding of the complex interactions between pharmacological lipid-lowering strategies and lifestyle interventions, ultimately guiding personalized management plans for patients with dyslipidaemia.

Inclusion Criteria:

• Age: 40-65 years
• LDL-C > 4.0 mmol/L.

Exclusion Criteria:

• Diagnosed with serious chronic disease including type 1 or 2 diabetes.
• Cancer.
• A history of atherosclerotic cardiovascular disease.
• A history of major depression or other severe psychiatric disorders.
• Severe renal dysfunction (creatinine clearance <30 mL/min).
• Severe hepatic impairment.
• Active pregnancy or breast feeding.
• Active cigarette or e-cigarette smoker.
• Regular (>2 hours pr week) aerobic high-intensity exercise training.

The above-mentioned are masked with regards to atorvastatin/placebo and not exercise/non-exercise

Statistical analysis of primary outcome will be blinded to the assessor.