Reactive oxygen species, the key link between diet and insulin resistance?

[Ripped Barbarian]

It is often thought and said that the primary cause of insulin resistance is too many carbs 'because it produces an insulin response and the excess insulin makes cells insulin resistant' as a direct effect.
It is true that eating too many carbs will make you insulin resistant but it is largely down to other factors rather than direct effects of insulin, quite simply if insulin itself was the problem then we'd all be diabetic before our 5th birthday, it would be a runaway reaction.
It is important to differentiate between transient and chronic (or peripheral IR) insulin resistance, the first occurs due to energy flux and requirements by the cell, adjusted by various hormones/kinase activity, i.e a 'stuffed' cell becomes insulin resistant to prevent more glucose entering, whereas the second is an actual breakdown in the mechanism of the cell, the cell membrane fluidity, the ability for glut-4 to be exposed etc.

'Too many carbs' has it's effects through an increase in fat storage metabolic side effects, increase in ROS generation.

Fructose for example does not have a large impact on insulin levels but has serious consequences for hepatic fat storage and creation of ROS, this is why you see increased uric acid levels in people on high fructose/sugar diets.

Insulin itself has shown to have effects on increasing oxidative stress in various studies so no doubt a chain reaction effect, one that would not occur with adequete antioxidant capability.

In fact the more research i do i consider that oxidative stress is the main player in modern cases of insulin resistance we are seeing and as part of metabolic syndrome.
Of course it has been known for a while the negative effects of oxidative stress on insulin resistance etc but i feel when people blame direct insulin reactions it is missing the main issue in modern diets.

Overproduction of ROS and underproduction/availability of antioxidants is of course the root of the problem.
Oxidative stress promotes several factors that lead to insulin resistance along with heart disease/cancer:

-Lipid peroxidation, especially important in cell membranes for fluidity!
-Increase in inflamation, nock on effects for cellular signalling/fluidity.
-Effects on kinase activity as follows:

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In vitro, ROS and oxidative stress lead to the activation of multiple serine kinase cascades[18]. The insulin signaling pathway offers a number of potential targets (substrates) of these activated kinases, including the insulin receptor (IR) and the family of IR substrate (IRS) proteins. For IRS-1 and -2, an increase in serine phosphorylation decreases the extent of tyrosine phosphorylation and is consistent with the attenuation of insulin action

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The role of serine kinase activation in oxidative stress-induced insulin resistance. A variety of stimuli, including hyperglycemia, elevated FFA levels, cytokines, and others, increase ROS (and RNS) production and oxidative stress. This results in the activation of multiple stress-sensitive serine/threonine (Ser/Thr) kinase signaling cascades such as IKK-ß and others (see text for details). Once activated, these kinases are able to phosphorylate multiple targets, such as the IR and IRS proteins (including IRS-1 and IRS-2). Increased phosphorylation of IR or IRS proteins on discrete serine or threonine sites (pS/T) decreases the extent of insulin-stimulated tyrosine phosphorylation (pY)[52,53]. Consequently, the association and/or activities of downstream signaling molecules (e.g., phosphatidylinositol 3-kinase [PI3K]) are decreased, resulting in reduced insulin action (insulin resistance)

http://www.medscape.com/viewarticle/448389_3

Various antioxidant promoting substances have been shown to have huge benefits on insulin sensitivity:
ALA, vit E and zinc, selenium and chromium for endogenous antioxidant production etc.
Polyphenol antioxidants like those in cinnamon bark....
Even whey protein with high cysteine content....

It's well known that people with iron overload disorder are at high risk of developing insulin resistance/diabetes.
Iron happens to be very pro-oxidative in excess.

There's a whole host of studies that you can find on google to support my views.

As far as diet and exercise goes i feel anything that increases antioxidant capability and decreases oxidative load (other than for short term hormetic effects) is a great way to boost inuslin sensitivity, prevent diabetes, heart disease and cancer.
I have found various studies that link high fat diets (as well as high refined carb diets in all fairness) with oxidative stress.

Low Aerobic Capacity and High-Fat Diet Contribute to Oxidative Stress and IRS-1 Degradation in the Kidney
High fat diet increases the incidence of orofacial dyskinesia and oxidative stress in specific brain regions of rats. | Fachinetto, R., Burger, M. E., Wagner, C., Wondracek, D. C., Brito, V. B., Nogueira, C. W., Ferreira, J., Rocha, J. B. T. | Pharma

And a hell of a lot more if you google.

Despite what has been promoted here fat oxidation (from a high fat diet) seems to produce a high level of ROS production (peroxides mostly) it's not the 'clean fuel' as has been promoted in the past.

Thoughts?

[NU_nutrition_TS]

A high fat diet that is below the threshold of carb intake that prevents ketosis is likely not a very 'oxidative' one as you will be using ketones and ketones are a 'clean burning' fuel. High levels of insulin are secreted due to a high level of carb intake and a high carb intake means you will be predominately burning glucose. It is glucose oxidation in the mitochondria that produces a high level of ROS - so it all links in. Carbs still do not get away blameless!

Again the studies you quote were on rats. Rat chow is notoriously high in refined carbs even when it is supposed to be a high fat option! Also, it merely says a 'high fat diet' it doesn't specify the type of fat. Again typical rat chow is made with vegetable oils as the source of fat.

[Ripped Barbarian]

You'll like this then

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Ketone bodies (KB) have been shown to prevent neurodegeneration in models of Parkinson's and Alzheimer's diseases, but the mechanisms underlying these effects remain unclear. One possibility is that KB may exert antioxidant activity. In the current study, we explored the effects of KB on rat neocortical neurons exposed to hydrogen peroxide (H(2)O(2)) or diamide - a thiol oxidant and activator of mitochondrial permeability transition (mPT). We found that:
(i) KB completely blocked large inward currents induced by either H(2)O(2) or diamide; (ii) KB significantly decreased the number of propidium iodide-labeled cells in neocortical slices after exposure to H(2)O(2) or diamide; (iii) KB significantly decreased reactive oxygen species (ROS) levels in dissociated neurons and in isolated neocortical mitochondria; (iv) the electrophysiological effects of KB in neurons exposed to H(2)O(2) or diamide were mimicked by bongkrekic acid and cyclosporin A, known inhibitors of mPT, as well as by catalase and DL - dithiothreitol, known antioxidants; (v) diamide alone did not significantly alter basal ROS levels in neurons, supporting previous studies indicating that diamide-induced neuronal injury may be mediated by mPT opening; and (vi) KB significantly increased the threshold for calcium-induced mPT in isolated mitochondria. Taken together, our data suggest that KB may prevent mPT and oxidative injury in neocortical neurons, most likely by decreasing mitochondrial ROS production.

FHA - Ketone bodies are protective against oxidative stress in neocortical neurons - Article Summary

http://www.ionchannels.org/showabstr...?pmid=17240074

[NU_nutrition_TS]

Here is an example of a typical laboratory rat chow note the sugar/starch and source of fat:

Polyunsaturated oils increase ROS unlike saturated fatty acids.

EDIT: Just found these technical specs on lab rodent diets:

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Strains showing optimum reproductive performance when fed high fat
diets should receive 5V03, while those not requiring high fat diets should
be fed Advanced Protocol® Verified PicoLab® Rodent 50 IF Diet - 5V02
when involved in protocols involving estrogen-sensitive parameters.

The nutrional analysis and ingredients list for the aforementioned 'high fat' rodent diet is:

Not exactly a 'high fat' diet in the human sense and the fat comes from soybean oil, a PUFA. Also loaded with refined carbs (60% of total calories).

I think your theory with regard to ROS has much merit but you should exercise caution where interpolating rat studies to humans, especially where the rat diet is not specifically detailed within the study to be able to draw meaningful comparisons

[NU_nutrition_TS]

RB: You might find this interesting:

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Redox negative feedback involving FOXO
ROS (and reactive nitrogen species, RNS) are not simply dangerous by-products, but essential
components of cell signalling pathways [53,54]. Low levels of ROS seem to promote growth,
whereas higher levels induce cell arrest [55]. ROS can active FOXO, which suggests that FOXO
act as a negative regulator on increased ROS production [42,56-58]. FOXO are also modulated by
AMPK – the archetypal energy sensor of the cell, which is itself activated by ROS [59,60]. FOXO
activity is suppressed by insulin signalling in the short term, but this suppression is lost in the
longer term – especially under stressful conditions, and involves a feed back loop that upregulates
components of the Akt insulin signalling pathway [57]. Hence, excessive growth signalling it tightly
modulated as it can result in excessive oxidative damage. Indeed, it has been proposed that
feeding is associated with increased oxidative stress and can be viewed as inflammatory [61].
Glucose can also directly modulate FOXO function via O-linked-N-acetylglucosamine (O-GlcNAc),
improving resistance to oxidative stress [62]. In C.elegans, overexpression of O-GlcNac
transferase (OGT) can result in insulin resistance, whereas knocking out its function may improve
insulin signalling and is associated with suppressed dauer formation and increased carbohydrate
storage, but decreased lipid storage [63]. Indeed, increased flux through the hexosamine pathway
has been known to be associated with insulin resistance (and thus, diabetes) for many years;
addition of O-GlcNac is now a well described process to modulate the function of multiple proteins
[64]. This would support the idea that FOXO can oppose insulin signalling and glucose-induced
oxidative stress.

From an evolutionary perspective, some FOXOs are known to translocate to the nucleus in times
of fasting and/or oxidative stress, so improving somatic protection, but reducing energy allocation to growth and reproduction. However, after extended fasting, there is evidence, at least in C.
elegans, that they translocate back out of the nucleus in what appears to be an Akt-Pi3K
dependent mechanism. The explanation for this appears to be that somatic protection comes at an
energy cost (e.g. manufacture of anti-oxidant proteins), and once anti-oxidant defences have been
improved, the process is downregulated [65]. Thus, continual growth signalling and excessive
calories might cause FOXO to remain active and thus continue to be active in the metabolic
syndrome.

FOXO and nature of thriftiness
Failure to eat is a strong negative selective pressure, which has likely led to an imbalance between
orexigenic (stronger) and anorexic (weaker) signals, leading to high feed-efficiency and a
propensity to store fat [66-68]. As both inflammation, and feeding (via increased Akt signalling),
might act to suppress FOXO activity, but FOXO activity may be important in resistance to stress
via suppression of ROS – it could be argued that FOXO must be a powerful counter-regulatory
mechanism. Certainly, TNF-α is known to activate FOXO, which can then induce apoptosis [69].
However, inhibitor of kappa B kinase (IκBK), which also activates nuclear factor kappa B (NF-κB),
can also inhibit members of the FOXO family [70], implying a finely tuned response around
modulation of potentially energy consuming immune responses. It is therefore of interest that a
high fat diet can induce a pro-inflammatory response in the hypothalamus and insulin resistance
[71], while chronically elevated levels of leptin can also induce leptin resistance – which may be
part of an obesity-driven vicious cycle [72]. These observations could be partly explained by FOXO
activity.

Two recent pieces of research suggest that redox is integral to the appetite/anorexic mechanism,
and integrate this action with the endocannabinoid system (ECS). Via activation of AMPK, ghrelin
results in increased mitochondrial oxidation of fatty acids, increased ROS and a concomitant
increase in anti-ROS mechanisms, including transcription of UCP-2 and increased mitochondrial
biogenesis. This has the overall effect of reducing mitochondrial membrane potential and ROS
production. Importantly, it appears that orexigenic neuropeptide Y/agouti-related protein (NPY &
AgRP) neurons become active in a low ROS situation, which is the opposite of anorexigenic pro-
opiomelanocortin/cocaine- and amphetamine-regulated transcript (POMC) cells, which appear to
rely more on glucose and are more active at higher ROS levels. Hence, the orexigenic circuit may
rely more on fatty acids, whereas the anorexic one relies more on carbohydrate [73]. In another
study, via activation of PKC, ghrelin was found to activate diacylglycerol lipase (DGL), which
increases 2-arachidonoylglycerol (2-AG), so activating the CB-1 receptor: this then auto-activates
itself in a positive feed-forward loop involving PKC again. Without the involvement of CB-1, ghrelin
becomes ineffective [74].

This data suggests that the ECS is involved in altering cellular redox and that this may link in with FOXO and mitochondrial function, both of which are involved in appetite control. Furthermore, it
also suggests that orexigenic circuits may well rely on lower levels of redox to function, whereas
anorexic ones rely on higher levels. Hence, excessive calorie intake, especially of high glycaemic
index carbohydrate, might induce the anorexic circuit to fail or down regulate to protect itself,
leaving the orexigenic one intact, as it has better oxidative stress resistance; it would also be more
likely to function during starvation, when lipids become the predominant fuel in the body. It would
also support the use of low carbohydrate diets, which can often reverse many symptoms of the
metabolic syndrome [75].

In summary, the above support the hypothesis that excessive insulin (and leptin) signalling can
increase oxidative stress. Hence, resisting the signalling is a vital counterbalance in survival and
fulfils a basic evolutionary paradigm of coupling food seeking and storage behaviour with
resistance to oxidative stress. Thus, FOXO may well epitomise thriftiness, and the default setting to
continual stress (e.g. over-eating) must be to maintain its activity.

Abstract | Lifestyle-induced metabolic inflexibility and accelerated ageing syndrome: insulin resistance, friend or foe?

[Ripped Barbarian]

Interesting stuff, i was just reading about UCP-2 in relation to mitochondrial control of ROS and how various metabolic states effect it's production

I have to admit my understanding of this area is currently, limited.
Whilst i can look at studies and associate obeseity/excess calories easily with increased insulin resistance/CHD through these mechanisms it is still quite hard to exactly point to isocaloric differences in macronutrient metabolism.
Clearly having a diet which provides mineral and vitamin precursors to allow swift ROS homeostasis and correct feedback mechanisms is vital but regarding metabolic fuel this is going to take some reading over!

Regarding the big picture i have seen studies that conclude that a high fat diet or fasting (fat as primary fuel) promotes a break down in ROS control mechanisms along with conclusions about excessive insulin and carbohydrates.

You've got no argument from me that a diet high in modern carbs is likely to cause a disruption to the system and promote insulin resistance/heart disease but i still think it is vitally important to address every factor, remember if something is a negative aspect it dosn't mean doing everything but is going to be entirely positive.

Humans may work best on a high protein diet for example, until we have read more i don't think we can say with certainty what is the optimum for reduced cellular aging/reduction in heart disease/excess insulin and other 'metabolic syndrome' or 'modern' illness.

I think we can safely agree that seed oils and chippy chips fried again and again in rape seed oil is a major dietary factor to avoid?!
High unsaturated fat is going to be far worse than high saturated for sure.

[NU_nutrition_TS]

Quote

Regarding the big picture i have seen studies that conclude that a high fat diet or fasting (fat as primary fuel) promotes a break down in ROS control mechanisms along with conclusions about excessive insulin and carbohydrates.

Don't forget that what a study (author) concludes and what the study (data) actually proves are often diametrically opposed! Researchers generally try to couch their conclusions in terms that won't rock the peer review boat and so tend to reflect the prevailing dogma. Also bear in mind that many of these studies do not specify what the fatty acid make-up of their 'high fat diet' is or whether carbohydrate content has been sufficiently lowered.

It is important to correlate what is concluded with what the raw data actually says and with the methods employed. Rat data should never be taken as 100% correlated with human responses to whatever protocol is under study. Animal trials are merely pre-cursors to human trials in most instances and are not the last word.

It is always important to cross-check study data with real-life results. An interesting observation by Gerald Reaven, who has done a lot of work on the insulin resistance syndrome (IRS) or syndrome X, is that the triglyceride-to-HDL ratio is often just as indicative of insulin sensitivity as is fasting insulin levels. If you look at the real life results of people following a high fat (especially of saturates) and low carb diet you will find they have low triglycerides and high HDL levels giving them a favourable ratio that, according to Reaven, indicate a high degree of insulin sensitivity. Incidentally he states a ratio >3 is the cutoff point for insulin sensitivity - you may recall from my own results that my triglyceride-to-HDL ratio was 1.25:2.20 or 0.57, well below the cut off point of 3!

[Ripped Barbarian]

Something interesting regarding protein intake (in rats)

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The maximum dietary protein intake that does not cause adverse effects in a healthy population is uncertain. We tested whether a high protein intake enhances oxidative stress. Adult rats were adapted to different casein-based diets containing either an adequate (13.8%; AP), medium (25.7%; MP), or high (51.3%; HP) level of crude protein; a fourth group received a HP diet but no RRR-{alpha}-tocopherol acetate (HP-toc). After 15 wk of feeding, plasma protein carbonyl concentration, liver lipid peroxide levels [thiobarbituric acid-reacting substances (TBARS)], reduced glutathione (GSH) status and leucine kinetics ([1-13C]leucine) were measured. Higher concentrations of protein carbonyls and TBARS were found in rats fed the AP and the HP-toc diets compared with those fed the MP and HP diets (P < 0.05). GSH concentrations in plasma did not differ but total blood GSH concentrations were significantly (P < 0.05) lower in rats fed the HP-toc diet compared with those fed the AP, MP and HP diets. Liver GSH concentrations were significantly (P < 0.01) lower in rats fed the AP diet compared with the other groups. Rates of postabsorptive leucine oxidation (LeuOX) and flux (QLeu) were positively correlated with the dietary protein level (for AP, MP, and HP, respectively: LeuOX, 74.9 ± 28.5, 109 ± 35.2, 142.3 ± 38.4 µmol/(kg · h); QLeu, 425 ± 102, 483 ± 82, 505 ± 80 µmol/(kg · h). Only HP-toc resulted in a significantly greater protein breakdown (PBLeu) and QLeu. No difference was seen in nonoxidative leucine disposal. Long-term intake of high protein diets did not increase variables of oxidative stress, in contrast to our initial hypothesis. An unexpected finding was that adequate protein feeding (AP) may in fact induce oxidative stress.

http://jn.nutrition.org/cgi/content/...ct/130/12/2889

Something in relation to atkins diet!

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…not all AGEs are even derived from glucose. Blood fats (triglycerides) can also cause the cross-linking of proteins, particularly if there’s a high level of oxidative stress: this is the chemistry that underlies the browning of a turkey skin as it roasts, even without a sweet, syrupy slather on its surface. As with blood sugar, diabetics usually have high triglyceride levels, and even many nondiabetic people would benefit from having their triglyceride levels brought down; but triglycerides also resemble blood sugar in being indispensable to normal function, so there’s only so far that such a strategy can be safely pursued.

LESS IS MORE…IS WORSE

And that’s not all: attempts to control levels of both these early precursors of AGEs, even by nonpharmacological means, can have perverse metabolic consequences.

For instance, one established effect of very low-carbohydrate diets of the Atkins type is to bring down both triglyceride levels and the body’s total exposure to carbohydrates, so some advocates have hypothesized that these diets would reduce a person’s AGE burden. Unfortunately, it turns out that the metabolic state that these diets induce (the notorious “ketosis”) has the unfortunate side effect of causing a jump in the production of the oxoaldehyde methylglycoxal, a major precursor of AGE’s that is also, ironically, produced within the cells of diabetic patients when they are forced to take in more glucose than they can immediately process. A recent study tested the size of this effect in healthy people who successfully followed the first two phases of the Atkins diet for a month, and who had the ketones in their urine to prove that they were sticking to the diet. These previously healthy people suffered a doubling of their methylglycoxal levels, leading to concentrations even worse than those seen in poorly controlled diabetics. Like other oxoaldehydes, methylglycoxal is far more chemically reactive than blood sugar (up to 40,000 times more reactive, in fact), and is known to cause wide-ranging damage in th body, of which AGE cross-links are but one example. This potentially makes the Atkins diet a recipe for accelerated AGEing, not a reprieve from it.

http://www.proteinpower.com/drmike/l...dative-stress/

The article goes on to work against this viewpoint stating that high triglycerides and glucose from a higher carb diet are far worse... an interesting read.

[NU_nutrition_TS]

How did they determine the protein quantities that they labelled 'adequate', 'moderate' and 'high'? How do these relate to protein intakes in humans? Seems fairly arbitrary to me!

In humans, a protein level that is roughly one third of total calories seems about right, in studies looking at the ability of the kidneys to optimally cope with the metabolic by-products, and would be termed 'high protein' by WHO standards.

[Ripped Barbarian]

Their protein level on the HP diet was 51.3%, which is considerably higher than average diets (25% is it?) thus is high protein.

I have stated before that i think humans evolved on a high protein diet (50%).