Year in Review

The metabolic dysfunction that characterizes obesity and type 2 diabetes mellitus affects not only the heart and kidneys, but also the liver. Although lifestyle modification remains the cornerstone in the management of metabolic liver diseases, the field has progressed this year, with a new definition, validation of non-invasive biomarkers and numerous clinical trials.

The year 2023 brought reports of highly effective glucagon-like peptide 1 (GLP1) mono-agonists or combinations with amylin receptor agonists. Results for monomolecular co-agonists that added glucagon receptor and/or glucose-dependent insulinotropic polypeptide (GIP) receptor agonism to GLP1 receptor activation were also published in 2023. Interestingly, antagonistic GIP receptor antibodies conjugated with a GLP1 agonist were also shown to be effective.

The pathophysiology of endometriosis is underpinned by a complex interplay of inflammatory processes that are responsible for the local and systemic effects of the condition. Recent studies delve further into this inflammatory interplay; using animal models, they identify potential therapeutic tools and remind us to look beyond the endometriotic lesions.

One hundred years after the Nobel prize was bestowed on Banting and McLeod for the ‘discovery’ of insulin, we are again seeing major evolutions in the management of type 1 diabetes mellitus, with the prospect of achieving disease control beyond mere management now becoming real. Here, we discuss the latest, most notable developments.

Over the past decade, technological advances have enabled cost-efficient, high-throughput analysis of different types of omics data in large human cohorts. Here, we explore insights into the pathophysiology of metabolic disorders revealed through multi-omics studies, discuss novel computational analysis techniques and look at the field’s future directions.

The year 2022 has been notable for game-changing early progress in clinical trials with stem cell islets; durable and promising 20-year data with long-term outcomes in clinical islet transplantation; and the development of locally protective or gene-editing-based approaches to avoid long-term immunosuppression.

Calorie restriction and timed dietary intake are two approaches known to increase lifespan or delay age-associated diseases. New studies reveal the importance of the ‘how much’ and ‘when’ of dietary intake in ageing modulation and collectively demonstrate how protection of the internal clock by diet can delay the ageing process.

Adipose tissue is highly versatile, dynamic and essential for metabolic health. In 2022, several exciting discoveries provided a high-resolution view of cellular composition and cell–cell communication within the adipose niche, and revealed how adipose tissue communicates with other organs and modulates metabolism during normal and pathophysiological states.

In 2022, the activation mechanism of TSH receptor (TSHR) by TSH and autoantibodies was demonstrated, monocarboxylate transporter 8 (MCT8) deficiency was corrected with gene therapy in mice and mutant thyroid hormone receptor α (TRα) was activated with a synthetic ligand. These results offer translational perspectives for patients with common and rare diseases affecting these proteins.

Glucagon-like peptide 1 (GLP1) analogues are licensed options for obesity, but new treatments are required to obtain better weight loss and to directly address other co-morbidities, such as non-alcoholic fatty liver disease. Research published in 2022 shows that co-agonist combinations of GLP1 with other hormones provide clinically important advances.

Metabolites have emerged as central regulators of biological function, but understanding mechanisms of metabolite regulation has proven challenging. In 2021 we have seen discoveries in the field of metabolite signalling motivated by a combination of scientific intuition and the elegant deployment of new technologies.

In 2021, several discoveries shed light on the pathomechanisms of β-cell failure during the initiation and progression of diabetes mellitus, and validated novel molecular targets for intervention. Moreover, the field of stem-cell-derived replacements for β-cells is rapidly advancing. These advances bring us closer to therapies to protect and/or regenerate β-cell mass.

Physical activity stimulates tissue crosstalk and provides powerful protection against cardiometabolic disease. This past year, several studies have expanded our knowledge of the secreted molecules regulated by physical activity, uncovered new circuits of cell and tissue crosstalk and provided fundamental insights into the mechanisms that underlie the cardiometabolic benefits of exercise.

Obesity and impaired metabolic health are important risk factors for severe COVID-19. Novel data indicate that these risk factors might also promote vaccine-breakthrough SARS-CoV-2 infections in fully vaccinated people. Here, these relationships are discussed and post-acute sequelae of COVID-19 that are related to obesity and impaired metabolic health are addressed.

In 2021, clinical trials reported the promising effects of incretins and a new class of dual glucagon-like peptide 1–glucose-dependent insulinotropic peptide receptor agonists in preventing and treating type 2 diabetes mellitus and obesity. These ‘twincretins’ will transform the prevention of obesity and type 2 diabetes mellitus and the care of people with these conditions.

Neuroendocrine neoplasms are derived from the diffuse endocrine system and represent a spectrum of tumours with a diverse range of molecular abnormalities, functionality and anatomical locations. Here, some key advances in molecular diagnosis, functional imaging and therapeutic strategies that have been published in 2020 are discussed.

Polycystic ovary syndrome (PCOS) is a prevalent endocrine disorder characterized by reproductive and metabolic disturbances. Androgen excess is a hallmark of PCOS, driving many of the phenotypic features. In 2020, several findings highlight altered metabolic pathways as an underlying biological mechanism in PCOS. These findings add to our understanding of the complex interaction between metabolic homeostasis and reproduction.

Heart failure and chronic kidney disease are frequent causes of morbidity and mortality in people with type 2 diabetes mellitus. Cardiovascular outcome trials have confirmed benefits of sodium–glucose co-transporter 2 inhibitors on cardiovascular events, cardiovascular deaths, hospitalization for heart failure and renal outcomes. These benefits now extend to people with and without type 2 diabetes mellitus.

Owing to the strong association of non-alcoholic fatty liver disease with obesity and cardiometabolic disease, in 2020 experts controversially proposed to rename this condition as ‘metabolic associated fatty liver disease’. Additional studies have elucidated new genetic and dietary modifiers of this disease. This knowledge is essential to improve diagnosis, risk-stratification and treatment.

The development and application of effective immunotherapies for type 1 diabetes mellitus has lagged behind our ability to identify and stage individuals in pre-clinical stages of disease. This Year in Review addresses advances in immunotherapy aimed towards prevention and our readiness to roll out screening in the broader population.