Thursday, October 31, 2013

Mitochondrial Dysfunction and Alzheimer's Disease

Alzheimer’s Disease 

Alzheimer’s disease (AD) is a neurodegenerative disease that mainly affects people over 75 [1].  Symptoms of AD include progressive memory loss and impaired cognitive function.  AD involves fairly widespread brain atrophy, especially in a part of the temporal lobe called the hippocampus (23% reduction) [2], which seems to be involved in spatial memory and the consolidation of short term memory to long term memory.  People with mild cognitive impairment (kind of like pre-AD) also have hippocampal atrophy (18% reduction) [2].


Mitochondrial Dysfunction in Alzheimer’s Disease 

People with AD show several signs of mitochondrial dysfunction:
 
  • They have more mtDNA mutations than age-matched controls [3] [4] [5], which was associated with an increase in amyloid-β and β-secretase activity [4]
  • Many people with AD have specific mtDNA mutations that aren’t found in age-matched controls [3] [4]
  • They have a lower rate of glucose metabolism in various brain regions [2] [6].  In addition healthy individuals with a maternal, but not paternal history of AD have a lower rate of glucose metabolism in cortex (mtDNA is maternally inherited) [7]
  • Both people with AD and MCI have elevated levels of markers for oxidative stress in the central nervous system and the periphery.  This may suggest that the source of oxidative stress is systemic [8] [9]
  • They have lower levels of mitochondria and mitochondrial gene expression in the brain [10] [11] 

Mitochondrial Dysfunction as a Cause of Alzheimer’s Disease 

There is some debate as to whether mitochondrial dysfunction is a cause or consequences of AD.  The ‘Amyloid Cascade Hypothesis’ suggests amyloid-β is the cause of AD and that the mitochondrial dysfunction seen in AD is simply a consequence of amyloid-β toxicity [12].  In addition, amyloid precursor protein has been found to accumulate in the mitochondria and impair their function [13].  However, mitochondrial oxidative stress occurs early in AD and prior to amyloid-β toxicity [14].  Oxidative stress increases amyloid precursor protein and amyloid-β, which is likely because amyloid-β seems to function as an antioxidant [12]. 

There is an animal model of AD (3xTg-AD mouse) where mitochondrial dysfunction is evident as early as 3 months of age and precedes AD-like pathology [15].  There is also a very nice in vitro study that used cytoplasmic hybrid (cybrid) cell lines, which were developed from human neuroblastoma cells deficient in mtDNA and then repopulating them with mitochondria from either AD patients or age-latched controls.  The cybrids with mitochondria from AD patients produced many AD-like pathologies, such as increased amyloid-β, oxidative stress and activation of apoptosis [16].  The cybrid model allows this study to show that mitochondrial dysfunction can independently cause AD and is sufficient to cause the disease (at least in vitro) 

The Mitochondria as a Therapeutic Target for Alzheimer’s Disease

Various strategies that stimulate mitochondrial biogenesis and/or promote oxidative phosphorylation appear to be somewhat therapeutic for AD:
 
  • A ketogenic diet improved verbal memory in people who have mild cognitive impairment [17] 
  • Calorie restriction (without changing micronutrient intake) reduced amyloid-β in the temporal lobe in an animal model of AD (Squirrel monkeys), which negatively correlated with the increase in Sirtuin-1 [18]
  • db/db mice are leptin resistant, insulin resistant and develop AD-like pathology and symptoms.  Metformin reduced AD-like brain pathology, but didn’t reduce cognitive impairment [19]
  • The combination of carnitine and lipoic acid improved memory in both old rats [20] and ApoE4 mice [21]
  • Coenzyme Q10 reduced oxidative stress in the brain, decreased Aβ levels and improved cognitive performance in an animal model of AD (Tg19959 mice) [22] 

The results of these studies aren’t as impressive as the studies in the Parkinson’s disease post.  Two possible reasons are that: AD is a more complex disease than PD and mitochondrial dysfunction has a lesser role in AD; these therapies were given later in the disease progression and the degenerative nature of AD means it’s harder to recover if started off worse.

Sunday, October 20, 2013

Strategies to Avoid Fainting While Donating Blood

High Iron

For me at least, an unfortunate consequence of being Paleo is that my iron levels increased.  I went Paleo in late December 2010, about a year after that (January 2012) I got a blood test back and my ferritin was 166 µg/L (µg/L=ng/ml.  No conversion necessary!), then one year later (January 2013) the blood test showed my ferritin went up to 220 µg/L and the other markers (serum iron, transferrin and saturation) also increased. 

Iron levels are regulated to some extent, though not quite as well as sodium, potassium or calcium.  As for why I have high iron, perhaps I have a polymorphism/etc (something genetic) that promotes iron storage or accumulation, or perhaps it’s simply due to being a male who eats a fairly nutrient dense diet and a non-starvation level of calories and this is another part of the mismatch where HGs would have bled and had other blood loses more often than we do (not that I buy into the whole ‘nasty, brutish, and short’ thing). 

So being familiar with the idea that having high ferritin levels isn’t good (see Chris Kresser’s talk below) I started donating blood (I know totally selfish, but if more people with high ferritin donated blood out of self-interest the blood banks would be fuller, there would be less chronic disease and medical expenses would be lower).  (Anthony Colpo talks about his experience with blood donation and ferritin here) 


The first time I donated was in July.  I was quite anxious about fainting and there were two occasions when I did feel like I was trending towards fainting, but I ended up not fainting and feeling fine shortly afterwards, it was only during those two periods. 

I stumbled across some papers about fainting and blood donors while doing research for a somewhat unrelated assignment*, which allowed me to better prepare myself for next blood donation, which was earlier this month. 

Some Notes on Fainting from Blood Donation: 

The frequency of fainting among blood donors is actually really low (0.1-0.3%) [1] (0.17%) [2].  Those 0.1-0.3% probably didn’t adequately prepare for the blood donation and/or have poorer health than you.  The statistics are strongly on your side 

Most fainting occurred around when the needle was taken out or shortly afterwards when people stand up [1].  Not sure why for the needle (maybe fear of needles?), but standing up is more obvious.  Our upright posture and big brains are quite a challenge for the cardiovascular system**.  When you stand there is a transient pooling of blood in the legs (of about 300-800mL) before compensatory responses kick in, then combine that with a loss of ~500mL of blood (10%) from the donation.  No rush, stand up when you’re ready 

Strategies to Avoid Feeling Dizzy or Fainting: 

Increase water and salt.  The Red Cross/Google searches/Yahoo Answers/etc really only tell you to eat and drink lots of water prior to donation.  In addition to a loss of ~320ml of water (because blood is mostly water) you also lose 1,200mg of sodium (to put this in perspective, the RDI is <2,300mg and the average person eats 3,000-4,000).  Not only would you want to offset that loss, but increasing sodium prior to blood donation should be helpful as it enhances water retention and increases plasma volume expansion [1] 

Reduce stress and focus on regular breathing.  Being anxious is counter-productive.  Most people who faint have an aversion to needles and/or blood and often tend to be on the more hypochondriac end of the spectrum.  Stress increases the respiratory rate which lowers CO2 levels.  Lower CO2 levels in the blood causes vasoconstriction of the blood vessels to the brain and vasodilation of the blood vessels to the muscles, which decreases blood flow to the brain while lowering blood pressure (the effect of stress on CO2 and CO2 on blood flow makes sense when you consider the evolutionary context of stress).  In addition, lower CO2 increases alkalinity, which reduces oxygen uptake by tissues (the Bohr effect).  Before I knew this, I found that focussing on my breathing increased my breathing rate.  If anything, you should decrease your breathing rate (without deep breaths or holding your breath) to increase CO2 levels.  Increasing having a meal with carbohydrate prior to blood donation could be helpful by increasing CO2 production. 

Tense the muscles of your lower-body.  This is to activate the muscle pumps to return blood from those areas back to the heart, to increase blood flow to the brain 

Sit/lie in as much of a horizontal position as you can (lying down is ideal).  This is to reduce hydrostatic pressure to make it easier for blood to get to the brain 

This study has a list of recommendations for donation centres but you (the donor) can apply some of them as well (just read the conclusion section) 

After implementing these strategies, the second time went really smoothly, of course it could have just been because I was less anxious the second time as it was no longer a new experience, but I like to think that the noral of the story is that: PubMed > Yahoo Answers 

* The assignment was to find out why someone fainted while doing a clean and jerk.  Just very briefly, the three main reasons were that the lifter hyperventilated prior to the lift (not excessively, more of a psych up), remained in a squatting position for a while and performed the valsalva manoeuvre.  The valsalva manoeuvre is unavoidable, but excessive breathing and prolonged squatting are not.  If you’re concerned about fainting while weightlifting I would suggest not doing the latter two.

** For more on the cardiovascular challenges of our vertical posture look at the tilt table test and read the comments 

*** Blood pressure medications may increase the risk of dizziness or fainting from blood donation.  Discuss with your doctor

Sunday, October 13, 2013

Other Paleolithic Diet Trials: Part 2

See Part 1 for the uncontrolled trials before 2010

A Palaeolithic-type diet causes strong tissue-specific effects on ectopic fat deposition in obese postmenopausal women (2013) 

10 healthy, post-menopausal women, with a BMI of (28-35) ate a Paleo diet for 5 weeks.  Participants were given prepared meal portions for breakfast, lunch and dinner that were roughly 30:40:30 (protein:fat:carbs).  The Paleo diet included "lean meat, fish, fruit, vegetables (including root vegetables), eggs and nuts", and excluded  "dairy products, cereals, beans, refined fats and sugar, added salt, bakery products and soft drinks were excluded".  The diet was ad libitum so they could have extra of the allowed foods.  Calories burned through exercise didn't change

Macronutrients
Baseline
Paleolithic
Energy (kcal)
2408
1888
Protein (%)
16.0
28.0
Fat (%)
SFA/MUFA/PUFA (%)
33.0
13.0/12.0/5.0
43.5
8.0/20.5/12.0
Carbohydrate (%)
Sucrose (%)
49.5
11.0
25.0
6.0


They lost weight (86.4 to 81.8) and reduced their blood pressure, heart rate, fasting glucose and insulin, HDL-C and LDL-C (by a similar proportion), HDL-P and LDL-P (by a similar proportion) and triglycerides (see table 1 and 3).  And as the title suggests, average liver fat decreased, which is probably responsible for the improvements in liver insulin sensitivity, although whole body insulin sensitivity and muscle fat stores (not necessarily bad) didn't improve

However, the increased protein and can partially explain the weight loss and the protein and weight loss can explain the reduction in liver fat.  Without a control group which lost a similar degree of weight, or unless the Paleo group was kept weight stable, you can't conclude that the Paleo diet had a special effect on liver fat.  It's odd that HDL-C and HDL-P decreased seeing as replacing carbs with fat, weight loss and lower triglycerides are three factors that would increase HDL-C (and perhaps HDL-P?)


(You may remember that this study came out earlier this year in May.  As expected, many in the anti-Paleo crowd linked it and the some in the Paleo community raised some really quite irrelevant objections.) 

43 Healthy participants (23 male, 20 female), in their early 30’s were asked to eat an ad libitum Paleo diet for 10 weeks and participate in a CrossFit-based, high-intensity circuit training exercise program 

Paleolithic Diet
“A Paleolithic diet, as first described by Eaton and Konner, was implemented for all study participants. Subjects were advised to increase their consumption of lean meat, fish, eggs, nuts, fruit, and vegetables and were instructed to strictly avoid all grains, dairy products, and legumes. All modern, processed foods including any form of processed sugar, soft drinks, and coffees were also excluded from the diets of the subjects. No specific macronutrient recommendations were made, as the study design wanted to closely mimic a real world model that would incorporate food choices made by the average consumer. Intake of specific proportion of food categories (e.g. animal vs. plant foods) was also not given.” 

We aren’t given much information on what the participants actually ate except for: “Analysis of 3-day diet recalls revealed that subjects were eating an average of 49.75% of daily caloric intake from fat, 13.1% of daily caloric intake from saturated fat, 672.7 mg of dietary cholesterol, and only 25 g of fiber per day.”  Which only came from 8 returned diet logs 

Results
Before
After 10 Weeks
Total Cholesterol (mg/dl)*
168.8
178.9
n-HDL (mg/dl)*
107.1
120.2
LDL (mg/dl)*
93.1
105.6
HDL (mg/dl)
61.7
58.7
Triglycerides (mg/dl)
70.0
73.0
TC/HDL*
3.0
3.3
Body Fat (%)*
24.3
20.7
Body Weight (lb)*
177.6
170.6
Relative VO2 Max (ml/kg/min)*
39.8
44.9
Oxygen Consumption (ml/min)*
3.18
3.46
* Significant 

Most of these results aren’t terribly surprising.  You would expect body fat % and weight to decrease with almost any diet + exercise plan, and expect relative VO2 max and oxygen consumption to increase from an exercise plan like Crossfit. 

As for the blood lipids: It’s impossible to know for sure what the participants ate previously and for that matter what they ate during the trial.  I’m just going to generalise from the 8 diet logs and assume on average they increased fat, SFA and lowered carbohydrates.  Although since SFA made up only a small portion of total fat they probably increased MUFA and/or PUFA as well.  From the macronutrients alone you would expect: 

  • Increased HDL-C and lower triglycerides, because replacing carbs with either SFA, MUFA or PUFA raises HDL-C and lowers triglycerides [1]
  • A lower total cholesterol to HDL-C ratio, because replacing carbs with any whole food fats reduces the ratio [1] 

You wouldn’t know what to expect with LDL-C and total cholesterol (TC) because SFA raises TC and LDL-C, MUFA decreases LDL-C by a small amount, but not TC and PUFA lowers TC and LDL-C.  In the table below I guessed what they previously ate and the MUFA and PUFA in their Paleo diet.  I could be horribly wrong, but the point is these guestimates suggest most of the increase in fat would have come from MUFAs and PUFAs, which would be expected to reduce TC and LDL-C (unless they tanked their thyroid doing low carb + Crossfit) 

Previous Diet
Paleo Diet
Fat (%)
33.5 [2] (US average)
50
SFA (%)
11 [2] (US average)
13
MUFA (%)
~15.5?
27?
PUFA (%)
~7?
10?

In the discussion, the author suggests active weight loss may explain why the HDL-C was lower than expected and why the triglycerides were higher than expected. 

But what about the LDL-C?  Perhaps the participants underreported eating SFA rich foods or they were previously eating oats, margarine and a lower SFA, higher PUFA duet (than the US average) to lower their cholesterol 

What I liked about the study is that it looked at the effect of a Paleo diet in healthy participants.  But at the end of the day where’s the pathology?  The tiny increase in LDL-C is not a big deal and the other lipids may have been confounded by active weight loss. 

* If one were only looking at the effect of macros, the results suggest that the participants replaced MUFA and PUFA with carbs

Sunday, October 6, 2013

Other Paleolithic Diet Trials: Part 1

In diet trials it’s important to have a control group to control for placebo-like effects (for example, you often hear about how the control group eats better, does more exercise and loses weight).  Preferably this group, or another group, will be a second experimental group to be able to compare one diet/food to another.  This is because you should only eat a certain amount of food, so it’s important to know what foods (and exercise programs as well) are ‘better’. 

The two Paleo diet trials I blogged about previously did this, and so you were able to compare one diet to another.  There are other Paleo diet trials and unfortunately these ones didn’t have a control group.

The effect of transition from traditional to urban life-style on the insulin secretory response in Australian Aborigines (1980)

In each study a small group (13 and 10) of Australian Aborigines who had T2D went foraging in the outback with some modern aids like rifles and fishing tackles. 

Their previous diet was pretty poor and high in refined foods and alcohol.  The estimated macronutrient compositions for the traditional diets varied from (P:F:C) 50:30:20 in the first study to 80:20:<5 in a coastal area and 54:13:33 in an inland area in the second study, which came mostly from animal foods, yams and honey.  The first study described food as being “…plentiful and at no time was the group undernourished” while the second study had calorie intakes averaging only 1200 per day.  They also had high levels of physical activity.  Both studies observed weight loss and quite impressive improvements in glucose tolerance, insulin sensitivity and triglyceride levels (interestingly cholesterol didn’t change). 

I don’t think you should conclude from these studies that the ‘Paleoness’ of the diet (↑ meat, fruit, veg and ↓ grains, dairy, legumes) was responsible for the changes.  Their original diet was so poor that almost anything would have been better and there were a number of confounding variables in the intervention such as an extremely high protein intake (50%), a very low calorie intake which may have not been ad libitum, an increase in physical activity and weight loss.  Also, since the traditional diets were so high in protein they would really only be suitable for short-term, low calorie, weight loss diets. 


24 Piglets post weaning were randomly allocated to a ‘Paleo diet’ (mostly fruit and vegetables with some meat) or a cereal based swine feed with some added rapeseed oil.  Guess which group did better

The Paleolithic group ended up weighing less, had less subcutaneous fat, lower diastolic blood pressure, were more insulin sensitive and had much lower CRP (82%).  Although the cereal group ate more calories and weighed more, they didn’t have a higher body temperature. 


14 Healthy participants (5 male, 9 female), aged 20-40, ate a Paleolithic diet for 3 weeks. 

The Paleolithic diet was: ad libitum amounts of fruits and vegetables, unsalted fish, seafood, lean meats and nuts and flaxseed or rapeseed oil; limited amounts of dried fruit, salted seafood, fatty meats, potatoes, honey and cured meats; and no grains, dairy, legumes and processed foods. 

Macronutrients
Baseline
Paleolithic
Energy (kcal)
2478
1584
Protein (%)*
13.5
23.9
Fat (%)
SFA*/MUFA/PUFA* (g)
29.6
31.3/26.4/4.6
35.8
15.0/28.9/13.4
Carbohydrate (%)
54.3
40.0

Despite the fewer calories, the Paleolithic diet was higher in vitamin B6, C, E and potassium, but lower in calcium and sodium.  Although diet data only came from 6 participants 

Weight, waist circumference, systolic blood pressure, and PAI-1 (a pro-thrombotic protein) decreased 


9 Overweight, but not obese, sedentary and healthy participants (6 male, 3 female) aged 38±12 ate a Paleolithic diet for 10 days.  The diet seemed to be mainly lean meat, fruit, non-starchy vegetables and lots of carrot juice (see table 2). 

Macronutrients
Baseline
Paleolithic
Energy (kcal)
2372
2699
Protein (g)*
107
198
Fat (g)
SFA*/MUFA/PUFA* (g)
99
32/33/10
96
16/46/30
Carbohydrate (g)
254
249

The average intakes of potassium, phosphates and magnesium were higher and intake of sodium was lower.  The average calcium intake wasn’t significantly lower but calcium excretion was, suggesting a positive calcium balance. 

Total cholesterol, LDL-C, triglycerides, fasting insulin, insulin resistance and diastolic blood pressure decreased (see table 3 and 4). 

What I liked about this study was that they tried to control for potential effects of weight loss by increasing calories if the participants started to lose weight.  While weight is an important factor in IR, CVD, etc, this study (and I’m sure others) show that weight is not the only factor. 

Why the calories needed to be higher to prevent weight loss could be due to the calories in fruits and vegetables being far less easily extracted than refined foods, a change in the body fat setpoint/leptin sensitivity and/or for another reason.

The impact of the stone age diet on gingival conditions in the absence of oral hygiene (2009) 

For 4 weeks, 10 participants without periodontitis lived in semi-hunter-gatherer conditions (similar tools, shelter and food) with some aids (some food such as grains, salt, honey, herbs and milk.  A hunter would shoot an animal to provide meat.  But they also had to gather food themselves).  They had no access to dental equipment to clean their teeth although some of them used twigs to clean their teeth

The average number of sites with 'bleeding on probing' decreased from 34.8% to 12.6%.  However, the average gingival index increased but not significantly, due to the increase in plaque scores (0.68 vs. 1.47), which is not surprising given the lack of dental equipment.  Figures 2 and 3 are two pictures of a participant's mouth (before and after) and show that the experiment increased plaque and stuff on the teeth, but reduced inflammation in the gums.  Bacterial count was higher in all 74 species (again not surprising), but there was a reduction in some pathogenic bacteria in the tongue that is likely due to an absence of  simple sugars (except some fruit and honey).  The participants also lost between 1-5 kg and had a reduction in blood pressure (given the conditions and that they were in Switzerland and had to make their own fire, they probably had a forced calorie deficit).

The researchers suggest that a near absence of simple sugars and increase in phytonutrients may have been responsible for the decrease in inflammation.  Since their diet had whole grains, including wheat, you couldn't use this as evidence against grains.  This could be a good example where we have the potential to be healthier than hunter-gatherers, unless we're meant to have plaque and stuff on our teeth

See Part 2 for the uncontrolled trials after 2010