Lecture 2 - Genes and food environment and gene x environment interactions Flashcards

(18 cards)

1
Q

What is the role of genes?

A
  • 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
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2
Q

What is Leptin?

A
  • 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
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3
Q

Study: the ob/ob mouse

A
  • 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)
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4
Q

How does Leptin influence weight in humans?

A
  • 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
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5
Q

How does leptin work in humans?

A
  • 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
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6
Q

Is leptin deficiency a monogenic cause for obesity?

A

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

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7
Q

How does ghrelin act as a hunger signal?

A
  • 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
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8
Q

What happens if you don’t have ghrelin?

A
  • 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
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9
Q

What is an obesogenic environment?

A
  • AN environment that promotes gaining weight and one that is not conducive to weight loss
  • Swinburn, egger et al., 1999
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10
Q

What are the features on an obesogenic environment?

A
  • Many eating opportunities (abundance)
  • Large portion sizes
  • Energy dense foods
  • Highly palatable foods
  • Food variety
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11
Q

What are the four groups in the NOVA classification of food (Monteiro, 2017)

A

1 - Unprocessed foods
2 - Processed culinary ingredients
3 - Processed foods
4 - Ultra-processed foods

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12
Q

What is are some critiques to the NOVA classification?

A
  • 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
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13
Q

What are some of the reasons for processing foods?

A
  • 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
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14
Q

Study: Lane et al., 2024

A

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

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15
Q

What types of foods have a positive relationship with multimorbidity? (cardiovascular disease, cancer, diabetes)

A
  • Animal - based products
  • Artificial and sugar-sweetened beverages
  • Sauces
  • Spreads
  • Condiments
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16
Q

How do UPF interact with Leptin?

A

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

17
Q

How do UPFs interact with ghrelin?

A

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

18
Q

How can we improve products? - real world application for the future of UPFs

A

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