NTRN Exam 1: Nutrition and Genetics

What two things determine human behavior?

• Nature: an individual’s genes
• Nurture: environment & social interactions

Much of human growth and development → continuous and complex interaction between heredity and environment

How many alleles do traits contain?

2 (one from mom and one from dad)

Genotype v Phenotype

• Genotype: the specific composition of an individual's gene

• Phenotype: the physical appearance

What kinds of things do genetics influence?

• Inherited Traits 

  • The influence of genetics 

    • Physical characteristics

    • Disease

    • Development

    • Personality

    • Rate of maturation 

    • Intelligence

EX:

• Allergic reactions 

  • Asthma

  • Food allergies

  • Hypersensitivity to insect stings 

• GI Tract 

  • Crohn's disease 

  • Celiac Disease 

• Joints 

  • Dislocation of hips 

  • Rheumatoid arthritis 

• Skin 

  • Psoriasis 

• Others 

  • Tone deafness

  • Sleep apnea 

  • Abundant sweating, especially on forehead, tip of those nose and upper lip while eating spicy or sour foods 

What are the three types of body types?

• Body types 

  • Endomorphs: short torso, wide chest and hips 

  • Ectomorphs: tall and slender with long thin bones and narrow chest and hips 

  • Mesomorphs: medium, muscular build

Discuss genetics and behavior

• Behavioral Traits 

  • A genetic component underlies many behavioral traits 

    • Sociability 

    • Emotionality 

    • Activity level 

  • But there are no genes specific for behavior 

    • The genes exert their influence on behavior through their effects at a more molecular level

Is eating a heritable trait?

• Eating is a heritable trait 

  • Studies show genetics influences: 

    •  Calories consumed 

    • Preference for nutrients and food items 

    • Meal frequency 

What two drives regulate food intake?

1. homeostatic pathway

2. hedonic pathway

What is the homeostatic pathway?

• Homeostatic Pathway

  • Controls energy balance by increasing the motivation to eat following depletion of energy stores 

    • But when energy stores are replenished, will decrease motivation to eat

What is the hedonic pathway?

• Hedonic Pathway 

  • Can override the homeostatic pathway during period of energy abundance by increasing the desire to eat highly palatable foods

What is ghrelin?

• Ghrelin: increases appetite

  • Increases secretion when stomach is empty; secretion stops when stomach is stretched/full 

    • Variants associated with obesity, metabolic syndrome and binge eating

What is leptin?

• Leptin: suppresses our appetite 

  • Secreted by adipose cells; opposed by ghrelin

What is CCK?

• CCK: suppresses appetite

  • Slows digestion/stomach emptying 

    • Variants associated with extreme meal size

What is dopamine? How is this related to hedonic regulation?

• Dopamine: neurotransmitter that helps control the brain's reward and pleasure centers 

• Emerging evidence – some individuals have addictive phenotypes resulting from enhanced genetic dopamine function 

  • Altered hedonic regulation

Discuss genes and obesity?

• Heritability of obesity is estimated between 40-70%

• Identification of obesity genes has been promoted by the study of syndromes that are marked by hyperphagia 

  • Hyperphagia 

  • Prader willi syndrome 

• Identified genes have been associated with homeostatic control and adipocyte differentiation 

• Small effect sizes on obesity 

  • Lifestyle has predominant influence 

Discuss genetics and taste

• Genetics and Taste 

  • Density of taste papillae

    • Thought to be genetically influenced

  • Salivary Composition 

    • Delivers taste molecules to receptors and increases binding

    • Breaks down some foods to release taste molecules

    • Satiety related hormones 

  • Sensitivity of taste receptors 

    • Genetic variation in the expression of taste receptors

      • Bitter taste 

What is a genetic disorder?

• Genetic disorder: disease caused by a DNA abnormality 

  • Not all are life threatening

  • Variation in onset 

  • Examples: 

    • Inborn errors of metabolism (e.g., methylmalonic Acidemia (unable to break down fats which leads to a buildup and can be lethal), phenylketonuria (PKU): individual is not able to break down amino acid phenylalanine which is found in all of our animal based foods → need to avoid eating it in their body bc they dont have the enzyme to break it down which can leave to buildup which is very dangerous, Galactosemia: cannot break down galactose)

    • Celiac Disease: autoimmune disease characterized by an intolerance to gluten in wheat, rye, barley

What is hemochromatosis?

• Hemochromatosis: lack of protein that helps regulate iron absorption

  • Can't break down iron which leads up to iron overload which is extremely toxic 

  • Extremely limit the amount of iron that they are consuming 

• Many of these are caused bt Single Nucleotide Polymorphisms (SNPs)

What are single nucleotide polymorphism?

• variation in a single nucleotide (DNA building block) in the genome 

• • Most common type of genetic variation among people
  – Normally occur throughout a person’s DNA
  – Average rate: 1 per every 300 nucleotides  ~10 million
  SNPS in the human genome
  • Example: SNP replaced cytosine
  with adenine, guanine & thymine

• Most SNPS are located in the DNA between genes 

  • Minimal impact on health/disease 

• Some SNPs occur within a gene or in a regulatory region near a gene 

  • May help predict

    • An individual's response to certain drugs 

    • Susceptibility to environmental factors 

    • Risk of developing certain diseases 

What are chromosomal abnormalities?

• Chromosomal Abnormalities aka known as structural abnormalities, are when part of an individual chromosome is: 

  • Missing

  • Extra 

  • Switched with another chromosome 

  • Flipped upside down 

• Can have many effects depending on the specific abnormality and the chromosomes effected 

Down Syndrome

• Down syndrome

  • 47 chromosomes instead of normal 46

    • Presence of all or part of 3rd copy of chromosome 21

  • Frequency of the disorder increases with age of mother 

    • As a woman ages the quality of her eggs decline 

  • Unusual physical features 

    • Face: flat face; folded eyes; protruding tongue

    • Short digits 

    • Harsh voice

  • Risk factor for weight gain 

Velocardiofacial syndrome

• Velocardiofacial syndrome (VCFS)

  • Often called Digeorge Syndrome

    • Cause by deletion of a small segment of chromosome 22 

      • Heart, speech and learning difficulties

    • Second to Down Syndrome as a cause for mental retardation 

    • Nutritional services

How is newborn screening important in terms of identifying disorders.

• Newborn Screening 

  • Early detection critical to prevent mental retardation 

    • Newborns in most states screened for genetic disorders within the first few hours of life

What is nutrigenomics?

The study of nutrient-gene interactions & the effects of
these interactions on health (nutritional genomics)
• Effect of nutrition on health at the molecular level
• Explores how nutritional components directly or
indirectly affect the human genome
– Changing expression of genes
– Genetic characteristics influence the effects of nutrients

Diet induced diseases can be:

Diet-induced diseases can be eventually prevented,
improved or eradicated
• Can identify who carries ‘problem’ genes
– Tailor a diet specifically for that individual
• Reduce risks of developing diet-related disease
• Possibly treat existing conditions