Dahman, Abrar
(2025)
Ginger, ethnicity and brown adipose tissue activity: investigating the thermogenic potential through in vitro and in vivo approaches.
PhD thesis, University of Nottingham.
Abstract
Background
The ongoing obesity pandemic affects millions of people worldwide, with the rapid increase in obesity rates among individuals from different age groups and ethnicities posing a major public health concern. Brown adipose tissue (BAT) is known to be present in neonates, to maintain body core temperature. Since the rediscovery of BAT in adults in small quantities and its ability to be activated using external stimuli, such as cold exposure, medication or food compounds, it has become a focus of research to maximise its potential anti-obesity benefits. Brown fat also plays a vital role in regulating energy and glucose homeostasis within the body through a process known as non-shivering thermogenesis.
Aim
This thesis aimed to expand knowledge of BAT physiology in response to food compounds by considering confounding factors such as ethnicity via a systematic review approach; in-vitro studies to assess the role of 6-gingerol (a bioactive compound found in fresh ginger) in inducing BAT-like activity; and using a non-invasive technique that measures supraclavicular skin temperature (TSCR) to assess the effects of gingerol on BAT activity.
Method
The systematic review protocol was registered with PROSPERO (CRD42023423461). A comprehensive search was conducted across three data bases (Cochrane, PubMed and Embase) using predefined keywords. Screening involved reviewing titles, abstracts and references to identify studies meeting the inclusion criteria. The search strategy had no restriction on language, publication date, region, gender or intervention type.
Cell culture experiments were conducted at the Biodiscovery Institute of the University of Nottingham (UON), using immortalised human mesenchymal stem cells (IHMSCs) and human dermal fibroblasts (HDFs). Adipogenesis was induced through: (1) non-viral gene delivery using the GAG-binding enhanced transduction (GET) system, for plasmid DNA and peptides; and (2) exposure to 6-gingerol (a bioactive compound found in fresh ginger) to assess its potential role in promoting BAT-like characteristics. Cellular transformation was evaluated using Oil Red O staining (lipid accumulation), qPCR (gene expression of BAT markers) and immunocytochemistry (protein detection)
For the experimental clinical study, participants (aged 18 -45 years, BMI 18.5- 40kg/m2) were recruited through word of mouth, an e-poster and physical posters at the University of Nottingham. Eligibility was determined based on informed consent and predefined criteria (FMHS 85-1022, V2.0:10.07.2023). A randomised, double-blind controlled study was conducted during the winter season in a controlled thermal setting within the Academic Imaging Suite, Queen’s Medical Centre, UoN. BAT activity was assessed using thermal imaging and the PPG stress flow machine to evaluate physiological responses following capsule ingestion.
Result
The first result of the systematic review and meta-analysis included in the final analysis four studies, selected from a total of 6,684. Across these studies, there was an equal representation of 44 Asian and 44 European participants, totalling 88 individuals, examined for BAT characteristics. The results showed no difference in BAT activity between healthy Asian and European male adults.
The second study examined the effect of increasing concentration of 6-gingerol on the mesenchymal stem cells (MSC) differentiated in adipogenesis media. The results showed that the cells reprogrammed into adipocytes with characteristics of BAT, suggesting a beige phenotype.
The third study was a double-blind controlled study conducted on 52 participants, with an equal number of males and females. No significant difference was observed in BAT activity, nor did PPG stress flow measurements indicate any changes in the sympathetic nervous system following ginger/placebo capsule ingestion in either group.
Conclusion
In conclusion, the systematic review found no significant difference in BAT activity between Asian and European individuals. A significant gap exists in this area, primarily due to the lack of robust studies comparing different ethnicities. The study conducted in this thesis shows that consuming ginger in the form of 6-gingerol does not have an acute effect on BAT thermogenesis in adults. Seasonal variation seems to play a role in influencing the study’s significance. However, treating cells with 6-gingerol may encourage the development of BAT characteristics in adipocytes.
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