Lecture 2 - Genes and food environment and gene x environment interactions Flashcards
(18 cards)
What is the role of genes?
- Instructions for cells to produce proteins
- Proteins perform particular jobs in the body
- A mutation or deletion in the DNA can have a knock-on effect to the protein and job it should perform
What is Leptin?
- A polypeptide hormone (protein)
Coded for by the ob gene (on chromosome 7) - Produced primarily in adipose tissue (fat cells)
- Can cross the blood-barrier to reach neuronal targets (e.g., hypothalamus)
- Influences appetite and energy expenditure
Study: the ob/ob mouse
- Ob/ob mice - recessive mutation of the ob gene that is responsible for leptin production
- Ob/ob mice cannot produce leptin
- Eats excessively and gains weight rapidly
- Leptin administration = reversal (Halaas et al., 1995)
How does Leptin influence weight in humans?
- Leptin should positively correlate with body fat (the more body fat, the more leptin)
- Case reports of children with congenital leptin deficiency = resulted in hyperphagia (constant hunger) and sever obesity
- Leptin therapy led to weight loss
How does leptin work in humans?
- Leptin binds to specific leptin receptors in the brain + peripheral tissues
- Acts on brain to regulate appetite by either activating the anorexigenic (appetite-diminishing) or orexigenic (appetite stimulating) neural circuitry
- Also interacts with the mesolimbic dopamine system -motivation and reward for feeding
Is leptin deficiency a monogenic cause for obesity?
Monogenic - controlled by a single gene
- Unlikely to account for the ‘obesity epidemic’ as the ob/ob mutation is very rare
- Most people living with obesity have higher leptin levels and not lower
How does ghrelin act as a hunger signal?
- Mainly in stomach but also in places such as the kidney, pituitary and hypothalamus
- Secreted by the stomach and reaches the brain by crossing the blood-brain barrier + transmits its signal through the vagal nerve
- By stimulating the activity of NPY?AGRP neurons and decreasing the activity of POMC and CART neurons, ghrelin increased appetite and food intake
What happens if you don’t have ghrelin?
- After bariatric-metabolic surgery plasma ghrelin concentration decreased significantly (Geloneze et al., 2003) - this could be partly responsible for the weight loss
- Mutant mice without the ghrelin gene, or ghrelin receptor gene still eat normally and maintain body weight and do not gain weight when fed a high fat palatable diet (Zigman et al., 2005)
- Eating is so important it is not left to a single mechanism
What is an obesogenic environment?
- AN environment that promotes gaining weight and one that is not conducive to weight loss
- Swinburn, egger et al., 1999
What are the features on an obesogenic environment?
- Many eating opportunities (abundance)
- Large portion sizes
- Energy dense foods
- Highly palatable foods
- Food variety
What are the four groups in the NOVA classification of food (Monteiro, 2017)
1 - Unprocessed foods
2 - Processed culinary ingredients
3 - Processed foods
4 - Ultra-processed foods
What is are some critiques to the NOVA classification?
- UPF very broad category
- Potential for misclassification (no clear distinction between ‘processed’ and ‘ultra-processed’)
- Disagreements between consumers and scientists on what an UPF is (Sadler et al., 2022)
- Misalignment with health ratings
What are some of the reasons for processing foods?
- Improved health and safety - makes food edible
- Improved nutritional quality
- Improved taste
- Lengthened shelf-life -> reduced food wastage
- Convenience
- Can be cheaper
KNORR AND AUGUSTIN 2021
Study: Lane et al., 2024
Found that there was a convincing link between consuming UPFs and:
- Mental health issues like anxiety
- Metabolic health issues such as obesity
- Cardiovascular disease related mortality
What types of foods have a positive relationship with multimorbidity? (cardiovascular disease, cancer, diabetes)
- Animal - based products
- Artificial and sugar-sweetened beverages
- Sauces
- Spreads
- Condiments
How do UPF interact with Leptin?
Fernandes, Rosa et al., 2023
- Unprocessed foods negatively related to leptin
- UPFs positively related
- UPF lead to leptin resistance
Hall et al., 2019 - No difference in leptin levels between:
- Baseline and UPF diet
- Baseline and unprocessed diet
- UPF diet and unprocessed diet
How do UPFs interact with ghrelin?
Hall et al., 2019 - No difference in active ghrelin levels between?
- UPF diet and unprocessed diet
- Baseline and UPF diet
Decrease in ghrelin levels from baseline to last days of unprocessed food diet
How can we improve products? - real world application for the future of UPFs
Knorr and Augustin, 2021 - Improvement of technologies to:
- Improve retention of nutrients instead of losing them
Improve bioavailability of nutrients
- Be more sustainable
Gibney and Forde, 2022 - Reformulation
- To enhance nutrient density
- To reduce HFSS and energy density
- To change sensory and physical aspects -> reduce risk of overconsumption