Ancestral Health Symposium 2012

I have been selected for giving a talk this August, in the Ancestral Health Symposium 2012, held in Harvard Law School. My 20-minute talk will be about Immunometabolism, where I will cover some basics of the immune system, the relationship between metabolism and immunity at a molecular level and how a paleo-type diet, coupled with other approaches, can be a powerful tool for controlling and preventing inflammatory and autoimmune diseases. I will discuss the effects of specific nutrients and food components on immune cell functioning, as well as some dietary suggestions based on individual symptoms. 


Given that Im a post-graduate student travelling from Peru and Im working full time on my thesis, I am looking for some financial help for travel expenses. Additionally, Im looking for some help finding places to stay for a reasonable price. 


If you are interested and find my work helpful, please send me an email to lucas@lucastafur.com for further information. Any help is greatly appreciated. 


Alternatively, you can send any donation through PayPal, to lucas@lucastafur.com. I have eliminated the "Donate" button because PayPal charges a commission that is not charged if you send the money directly to my email from the PayPal website.

Adipose tissue & Immunity: The basics 1

Obesity has been, and its still seen, as primarily a metabolic disease. Obesity results from increased energy intake and decreased energy expenditure, that is, a positive energy balance for a prolonged time. By this logic, to cure obesity and associated diseases, one must restrict calories and/or do more exercise. While this approach works (calorie restriction being the key player), it does not solve the cause of obesity in the first place. This has been shown by numerous evidence that finds that even after weight loss, there is still some metabolic dysfunction in previously obese people. Some obese people can't fully recover. This underscores a common problem in modern health science: clinicians and health practitioners only focus on the proximate cause and not in the ultimate cause (for an interesting read on the subject, see this article). Moreover, obesity is just the tip of the iceberg. We have evolved mechanisms to prevent the development of a rather unadvantageous phenotype. Obesity occurs when these mechanisms start to fail, such as when pathological insulin resistance and leptin resistance develop. 

The obvious cause of obesity is the storage of excess energy as fat tissue. In this manner, excess energy causes an increased fat mass and problems start to arise due to the accumulation of excess body fat. While this statement is true, there is recent evidence that suggests that energy excess has also peripheral effects in cells that were previously unrelated to obesity; in particular, immune cells. 

Immunometabolism

Immunometabolism refers to "the interplay between immunological and metabolic processes" (1). Traditionally, the immune system and metabolic processes have been viewed as different, non-related systems. Now, research findings suggest that this is not the case, on the contrary, both are very related and understanding their interplay is essential for preventing and treating metabolic disorders.

The hypothesis that the immune system is involved in the pathogenesis of obesity started from the findings that targeting proteins which are part of inflammatory cellular pathways ameliorated or prevented the development of obesity and insulin resistance. For instance, Uysal, et al. (2) showed that a null mutation of the TNF-alpha and its two receptor genes improved insulin sensitivity in diet-induced obesity and in ob/ob mice. This confirmed previous in vitro evidence linking TNF-alpha with insulin resistance in adipocytes (3). Interest began to increase with the discovery and characterization of adipocytokines, as well as the finding that the adipose tissue secretes inflammatory cytokines. Adipocytokines are cytokines produced mainly (but not exclusively) in the adipose tissue, and include adiponectin, leptin, resistin and visfatin; being the first two the main adipocytokines produced. Other cytokines secreted by adipocytes are TNF-alpha, IL-6, IL-1 and CCL2; as well as other proteins, including PAI-1 and some complement factors. The table below shows some immune and metabolic effects of the main cytokines discovered, as well as their potential role on inflammation (modified from Tilg & Moschen, 2006). 

Adipocytokine	Effect on inflammation	Levels in obesity	Immunity	Metabolism
Adiponectin	Anti-inflammatory	Decreased	↓NFκB ↓TNF ↓Phagocytic activity (macrophages) ↑IL-10 ↑IL-1RA ↓IFN-γ	↓Hyperglycemia ↓FFA ↑Insulin sensitivity ↑β-oxidation ↓SREBP1c ↑AMPK
Leptin	Pro-inflammatory	Increased	↑TNF ↑IL-6 ↑IL-12 ↑CCL2 ↑Th1 (IL-2, IFN-γ) ↓Th2 (IL-4) ↑ROS ↑Chemotaxis ↑NK-cell function ↑Lymphopoiesis ↑Thymocyte survival ↑T-cell proliferation	↑Energy expenditure ↑Satiety ↑Insulin sensitivity
Resistin	Pro-inflammatory	Increased	↑NFκB ↑TNF ↑IL-6 ↑IL-1 ↑IL-12 ↑CCL2 ↑VCAM1 ↑ICAM1	↑Hepatic insulin resistance
Visfatin	Pro-inflammatory	Increased	↑IL-6 ↑IL-8 ↑IL-1β ↑TNF ↑ICAM-1 ↑IL-10, IL-1Ra (high concentrations)	↓Insulin resistance

The adipose tissue as an immune organ

Besides the role of pro-inflammatory cytokines produced by the adipose tissue, research has shown that obesity alters the function of several immune cells. In an elegant study, Caspar-Bauguil, et al. (4) found that immune cells are present in adipose tissue from mice, but their characteristics are different from other tissues, sharing some common ancestral features with hepatic immune cells. Specifically, the adipose tissue (levels of specific cell populations varying in different anatomical sites) shows both innate and adaptive features, such as the presence of Natural Killer cells (NK), NKT cells and delta-gamma T cells for the former and the presence of lymph nodes, B-cells and alpha-beta T-cells for the latter. This led the authors to propose that the adipose tissue (specially the epididymal adipose tissue) is an ancestral immune organ, due to the fact that delta-gamma T cells are thought to represent an evolutionary and functional bridge between the innate and adaptive immune systems. In addition, inguinal fat contained more adaptive immune cells. Not surprisingly, inducing obesity produced some changes in immune cells: NK cells in epididymal fat were decreased, whereas delta-gamma T cells were increased in inguinal fat and lymph nodes. 

The adipose tissue has site-specific properties and adipocytes interact in a paracrine fashion with adjacent lymphoid cells. Adipocytes near a lymph node are called "perinodal", and show differences from adipocytes far from lymph nodes (5, 6):

• They are smaller and size increases in a gradient manner from the node.
• Lipids extracted from perinodal adipose tissue contain proportionately more PUFAs and less SFA than those further from nodes or nodeless depots, proportion which is not significantly affected by diet (perinodal adipose tissue still has more PUFAs than nodeless adipose tissue). 
• Perinodal adipocytes influence the lipid composition of dendritic cells (and other lymphoid cells) found in lymph nodes, which suggests that perinodal adipocytes provide energy to immune cells for their activity.
• Following chronic immune stimulation, ratios of omega-6/omega-3 PUFA converge in perinodal adipocytes, probably for providing more substrates for ecosanoid and docosanoid synthesis.  
• Perinodal adipocytes are very sensitive to cytokines and noradrenaline, compared to adipocytes from other sites. 

Diet can influence the activity of perinodal adipocytes and associated immune cells. For example, Mattacks, et al. (7) compared the effect of feeding beef suet (mostly saturated and monounsaturated fat), sunflower oil (mostly omega-6 PUFA) and fish oil (mostly omega-3 PUFA) on the response of mesenteric, omental, popliteal and perirenal adipocytes to experimentally-induced local inflammation in guinea pigs. They found that basal lipolysis from sunflower oil-fed pigs was higher and lipolysis from perinodal adipocytes after incubation with noradrenaline was increased, compared with the other groups. The same authors found that the addition of sunflower seed oil (20%) to chow increased the number of dendritic cells in all adipose tissue samples, after stimulation with LPS (8).

Infiltration of immune cells to adipose tissue is now an accepted phenomenon during obesity. It seems that CD4+ T lymphocytes are recruited to adipose tissue first, coinciding with the appearance of glucose intolerance and reduced insulin sensitivity, while macrophages accumulate at late stages of obesity-induced insulin resistance (9, 10). Infiltration of B-cells occur rapidly in mice, before any significant change in body fat mass (10).

Innate immunity and adipose tissue

As has been mentioned, some adipose tissue show the presence of innate immune cells. One striking fact is that adipocytes and macrophages show similar characteristics. Weisberg, et al. (11) found that the expression of 1,304 transcripts in perigonadal adipose tissue from different mice correlated significantly with body mass. Of the 100 most significantly correlated genes, 30% encoded macrophage specific proteins. In mice, the adipose tissue is a major source of IL-6 during systemic inflammation produced by LPS (12). The tight relationship between adipocytes and monocytes/macrophages is exemplified by C3a. After activation of the alternative complement pathway, C3a induces mast cell degranulation and an immune response. This protein is also produced by adipocytes and the N-terminal cleavage of its alpha chain through the interaction of complement factors B and adipsin, followed by C-terminal arginine cleavage by serum carboxipeptidase N produces acylation stimulating protein (ASP) or C3adesArg, which is an important regulator of triglyceride synthesis. Moreover, C3a (ASP precursor) can also have metabolic effects: its receptor, C3aR, is expressed on both monocytes-macrophages and adipocytes. C3aR null mice are transiently resistant to diet-induced obesity, and are protected from diet-induced insulin resistance and hepatic steatosis, showing improved insulin sensitivity compared to wild-type mice (13). This was accompanied by a decrease in macrophage infiltration to adipose tissue, plasma cytokine levels and a polarization of macrophages towards a M1 phenotype (see below).

Toll-like receptors (TLR) are pattern recognition molecules with an essential function recognizing pathogens via pathogen-associated molecular patterns (PAMPs). Several types of TLRs are expressed by pre- and mature murine adipocytes, but mature adipocytes seem to be more responsive to a broader spectrum of TRL ligands (14). LPS triggers the secretion of IL-6 and different chemokines (CCL2, CCL5 and CCL11) and this inflammatory response appears to be based mainly on preadipocytes. The ultimate result of the activation of TLRs in adipocytes is the secretion of inflammatory cytokines via activation of NFkB signaling. Accordingly, LPS increases the expression of TLR2, TRAF-6 and NFkB in human adipose tissue, and increased levels of these markers, as well as LPS, is observed in type 2 diabetic patients (15). The finding that mice with defects on different TLRs are protected from obesity and insulin resistance supports the role of TRLs in the development of metabolic dysregulation (16, 17, 18, 19). Additionally, it suggests that different inflammatory stimuli act in the adipose tissue via different TLRs.

Macrophages infiltrating the adipose tissue can have two potential sources: those differentiated from bone-marrow-derived monocytes which reach the adipose tissue from the systemic circulation or by trans-differentiation from local adipose tissue preadipocytes and mesenchymal stem cells (14). Diapedesis of monocytes is stimulated by chemoattractants secreted by adipocytes (CCL2, CCL5, MIF and MIP1a) and locally produced macrophage colony stimulating factor (M-CSF) supports differentiation and maturation of monocytes into macrophages. On the other hand, both adipocyte and macrophage differentiation and function is controlled by PPAR-gamma. In addition, adipocytes also express macrophage-specific genes (20). This suggests that both cell types arise from a common precursor cell, and trans-differentiation of adipocytes into macrophages is supported by the findings of Charriere, et al. (21): preadipocytes are able to convert into macrophage-like cells, judging by specific antigens and the phagocytic index. Similar findings have been observed in other studies (22, 23), which report that preadipocytes can phagocyte and kill micro-organisms. 

Macrophages can show different activities depending on their phenotype. Classically activated macrophages (M1) respond to products derived from or associated with bacterial infections, like LPS and IFN-gamma. These macrophages are characterized by a highly inflammatory phenotype, displaying high phagocytic and bactericidal potential. Alternatively activated macrophages (M2) are induced in response to products from or associated with parasitic infections, such as Schistosoma egg antigen and Th2-type cytokines like IL-4 and IL-13 (24). M2 stimulate tissue repair and remodeling. Contrary to what was thought, adipose tissue from lean animals does have macrophages. However, obesity, besides promoting infiltration and migration of macrophages, induces a shift in macrophage balance towards M1 phenotype (25). In fact, obesity shifts the adipose M2:M1 ratio  from 4:1 in normal mice to 1.2:1 (26). Th2-type cytokines derived from the adipose tissue (IL-13 and IL-4) regulate macrophage polarization, favoring alternative activation (27). M2 development is also promoted by IL-10 (28). 

The role of other innate cells is not well characterized. It has been seen that peripheral natural killer (NK) cell levels in unhealthy obese patients is reduced compared with healthy obese, and NK cells from these patients show increased levels of inhibitory markers (CD158b and NKB1), but expression of CD69, a marker of NK activation (29). This suggests that although activated, NK cells from unhealthy obese patients cannot function properly. In visceral adipose tissue from obese subjects, there is an increase in NK cells compared to subcutaneous fat (30). Another type of innate cells, natural killer T (NKT) cells , which are T-like innate cells capable of producing both Th-1 and Th-2 type cytokines have been implicated in the inflammatory environment seen in obesity. Mice lacking NKT cells show reduced macrophage infiltration in response to a high-fat diet, and activation of NKT cells by alpha-galactosylceramide exacerbates glucose intolerance, macrophage infiltration and cytokine gene expression in diet-induced obese mice (31). However, the effects of NKT cells on obesity and insulin resistance seem to be dependent on CD8+ T cells (32). 

Summary

Interrelationship between the adipose tissue and the immune system. The adipose tissue (AT) secretes  adipocytokines (adiponectin, resistin, leptin, visfatin, among others) and conventional cytokines (TNF-a, IFN-gamma. IL-6, etc.), which influence metabolism and immunity. Cells from the innate and adaptive immune system are present in AT, and are fueled by perinodal adipocytes. Adipocytokines influence the function of immune cells, and cytokines secreted both by adipocytes and immune cells regulate the inflammatory milieu of the AT. Nutrition, by regulating fat mass and lipid composition, has direct effects on the function of immune cells.

Schäffler A, & Schölmerich J (2010). Innate immunity and adipose tissue biology. Trends in immunology, 31 (6), 228-35 PMID: 20434953 

Pond CM (2005). Adipose tissue and the immune system. Prostaglandins, leukotrienes, and essential fatty acids, 73 (1), 17-30 PMID: 15946832

Safe starches, blood glucose and insulin

A reader asked me recently about a subject which is confusing many people in the paleosphere. 

"Jaminet in his debate with Rosedale suggests higher carb diets tend to lower blood sugar whereas low carb diets, RAISE it. Can you help me untangle what is going on here? It makes it sound like the more carbs you eat the better your blood sugar levels which does not seem right to me. Clearly, an important health goal is achieving low blood glucose so I would want to know what is the best way to eat to control them. 

I always assumed that the less sugar you eat, the less blood sugar you'll have. Is there a threshold? If Jaminet is correct, then shouldn't we see a higher fasting glucose associated with ketogenic diets that are totally carb restricted vs higher carb diets? I know excess protein might be converted into glucose but if you followed a ketogenic diet with low protein would you still see the rise in blood glucose? 

What is the mechanism through which blood glucose is being lowered in high carbers? Do they secrete more insulin to deal with it hence lower blood glucose? Would their insulin levels therefore be higher even if blood glucose was relatively low? Which is worse for health- low glucose/high insulin or moderate glucose/low insulin? 

What is the mechanism through which some cancers are being suppressed with ketogenic diets if not through lowered blood glucose? Is there something else going on?"

These are very important questions as they raise some concern in people which utilize a low carbohydrate diet for controlling their blood glucose (BG). Before trying to elaborate an answer, there are some facts that must be kept in mind:

• Hyperglycemia is not a disease, it is a symptom. 
• BG levels can be affected by non-dietary factors.
• The two principal energy substrates for humans (glucose and free fatty acids (FFA)) compete with each other for their utilization.
• Calories matter.
• There are differences between physiological insulin resistance (PIR) and pathological insulin resistance (PaIR). The term "insulin resistance" is very vague, it doesn't define explicitly which tissue(s) is IR.

The first issue to adress is whether ketogenic diets raise BG levels. The only evidence I have seen for this happening is in anecdotes from people in the internet. But if we want to have an objective look at the subect, we must see what happens in studies done with ketogenic diets (I will use low carbohydrate and ketogenic diets equally). 

Ketogenic diets and blood glucose levels

Most studies done on ketogenic diets are short-term and involve weight loss. All of them show a reduction in BG and insulin levels. A study by Grieb et al. (1) found that people eating an optimal diet (Kwasniewski) had on average a BG level of 87.9mg/dL, which is in the normal range; and very low values of HOMA-IR. Sharman et al. (2) have shown that the metabolic benefits of carbohydrate restriction are independent of weight loss. Given the evidence, it is only possible to speculate about the mechanisms by which BG levels rise in some people eating a ketogenic diet.

The goal of a ketogenic diet is to simulate fasting, but without the negative effects of prolonged nutrient restriction. Before going on, it is pertinent to remember the Randle Cycle (3):

In short, both FFA and glucose compete with each other for their uptake and oxidation. This can be translated as when BG is high, FFA utilization is low; and when BG is low, FFA utilization is high. Ketogenic diets are characterized by low BG levels, in part because of a drastic reduction in exongeous glucose. In turn, plasma FFA rise from dietary and endogenous sources (the contribution of each one depends on energy balance). During this scenario, plasma ketone bodies also rise. So we have the following metabolic milieu:

Cellular effects of a fasting-type metabolism

For exerting it metabolic effects, insulin needs to first bind its receptor (the insulin receptor, IR). Upon binding, insulin triggers an intracellular signaling cascade, which influences both the function of intracellular proteins and gene expression. The signaling pathway triggered by the binding of insulin include the recruitment of the IRS (insulin receptor substrate) to the cytosolic part of the insulin receptor dimer. The signaling cascade stimulated by insulin is essential for its function. If proteins involved in this signaling pathway are inhibited, there will be no cellular response to the binding of insulin and the activation of IR.

One level of inhibition of glucose utilization by FFA involves the inhibition of GLUT4 translocation to the plasma membrane. The translocation of GLUT4 is stimulated by insulin, by activation of IRS, PI3K and other proteins (4, 5). In vitro studies have shown that palmitate, the main fatty acid stored in mammalian adipose tissue, inhibits GLUT4 translocation and activity (6, 7). This results in reduced glucose uptake in skeletal muscle.

Inactivation of PDH (pyruvate dehydrogenase) is one of the most important mechanisms for inhibition of glucose oxidation  by FFA. PDH activity is controlled by phosphorylation, by PDK (pyruvate dehydrogenase kinase) and PDP (pyruvate dehydrogenase phosphatase). Phosphorylation by PDK inactivates PDH, while dephosphorylation by PDP activates it. Fatty acid oxidation increases the mitochondrial ratios of [acetyl-CoA]/[CoA] and [NADH]/[NAD+], which inhibit PDH. Low carbohydrate diets have shown to reduce muscle PDH and increase PDK (8, 9), effects which are reversed by a carbohydrate refeeding (10). Fatty acids also increase the concentration of cytosolic citrate, which inhibits 6-phosphofructo-1-kinase, providing another mechanism of inhibition of glucose oxidation (3). Fatty acids can reduce phosphorylation of IRS-1 (11), GSK-3b and PKB/Akt (12), thereby acting also downstream of IR and IRS.

The metabolic response to fasting can show what are the effects on insulin signaling of very high levels of plasma FFA and ketone bodies, but within a physiological range. In a very interesting study, Soeters et al (13) found that insulin-mediated peripheral glucose uptake after 62h of fasting was significantly lower compared to 14h of fasting. They also found that after 62h of fasting, Akt phosphorylation at Ser473 and AS160 phosphorylation at Thr642 were reduced. This implies that insulin signaling was attenuated (reduced phosphorylation of Akt) as well as glucose uptake (phosphorylation of AS160 is involved in the translocation of GLUT4). The authors concluded:

"(...) it is possible that pAKT-ser⁴⁷³ is involved in the physiological adaptation to fasting, inducing a reduction in peripheral glucose uptake and protecting the body from hypoglycemia."

Intramyocellular triglyceride accumulation is thought to mediate fatty acid insulin resistance. This is one way by which some authors think that a high-fat diet leads to insulin resistance. Compared to fasting (67h) a very low carbohydrate diet (eucaloric) produces the same amount of IMTG accumulation, both produce glucose intolerance and reductions in insulin sensitivity (14). Thus, the factor for triggering this metabolic response seems to be the absence (or drastic reduction) in glucose availability (my bolds):

"Thus, we suggest that dietary-induced IMTG accumulation and insulin resistance in healthy humans may be largely influenced by circulating FFAs, whose availability (in turn) is regulated by dietary CHO intake. (...) our study provides support for the hypothesis that the physiological trigger for this coupling in the healthy individual may be a short-term challenge to dietary CHO availability. That we have observed these diabetogenic alterations in a physically fit population, which is purported to be insulin sensitive yet exhibits high IMTG concentrations (the ‘athlete paradox’) (Goodpaster et al. 2001), supports our contention that they represent an adaptive rather than pathological response. This substantiates our previous assertion that alterations in glucose tolerance and insulin sensitivity associated with dynamic changes to the plasma and/or lean tissue lipid profile are part of a normal co-ordinated adaptation to short-term changes in food availability (Stannard & Johnson, 2004) and perhaps, more specifically, to fluctuations of dietary CHO availability. (...) This short-term alteration is teleologically sound because it limits competition between skeletal muscle and glucose obligate tissues for circulating glucose substrate when its availability becomes limited. Irrespective of a causal relationship, the coupling between IMTG accumulation and reduced insulin sensitivity may also represent a co-ordinated adaptive (non-pathological) response to CHO stress  (Johnson et al. 2003). A concomitant resistance in muscle to the effects of insulin on glucose uptake during CHO stress maintains normoglycaemia and thus the preservation of plasma glucose for use by the CNS and glucose-obligate tissues (Reaven, 1998). Dissociation of insulin action by way of muscle insulin resistance rather than attenuation of insulin secretion means that residual circulating insulin levels can be maintained (Klein et al. 1993), thereby preventing rampant proteolysis (Fryburg et al. 1990), lipolysis (Kather et al. 1985) and perhaps hepatic glucose release, whilst unnecessary uptake of blood glucose by muscle is prevented."

So, from the studies above, we can conclude that:

• FFA supress glucose uptake and oxidation, resulting in muscular insulin resistance, without reducing insulin secretion.
• These effects seem to be dependent on dietary carbohydrate restriction.
• FFA-induced muscular insulin resistance is a physiological response to low availability of glucose. 
• Under normal conditions, this serves to maintain adequate BG levels. When FFA are in excess, there might be a rise in BG levels, because oxidation and release of FFA are not coupled. This leads to insulin resistance in other tissues like the liver (15), consequently failing to control hepatic glucose output.

Blood glucose levels and high carbohydrate diets

Without any biochemical explanation, logic dictates that if we eat a high carbohydrate diet, glucose oxidation pathways are stimulated. This is the opposite of what we observe with carbohydrate restriction, that is, stimulation of insulin signaling. Glucose and insulin both regulate GLUT4 and GLUT1 in muscle cells (16) to increase glucose uptake. The Randle cycle dictates that glucose stimulates its own oxidation and reduces fatty acid utilization. As shown above, glucose reduces PDK and increases PDH. Insulin inhibits lipolysis, further facilitating glucose oxidation. In healthy subjects, a high carbohydrate-low fat diet can improve insulin sensitivity (17, 18). It makes sense, carbohydrates supress fat oxidation and increse glucose oxidation. Overall, there should not be a rise in BG levels on a 24h basis, if anything, we can expect a reduction, because we are utilizing glucose as our main substrate. 

The common ground: calorie restriction

Until now, we have seen that carbohydrates stimulate glucose utilization (insulin sensitivity) and that FFA supress it. How can then a ketogenic diet produce such good results in people with diabetes? Diabetes and MetSyn are characterized by lipotoxicity and glucotoxicity (19). This means that there is an abnormal level of plasma FFA and glucose, produced by PaIR. Insulin cant supress hepatic glucose output, muscle cells do not respond to insulin, and adipocytes liberate FFA in an uncontrolled fashion. In very simple terms, there is an excess of both energy substrates, each one inhibiting the utilization of the other. This scenario can be improved both by restricting fat (thereby increasing glucose utilization) or restricting carbohydrates (increasing fat utilization). In either case, calories must be restricted (directly or indirectly). So, people who show signs of glucose intolerance and switch to a ketogenic diet can improve their BG and insulin levels (by reducing glucotoxicity), but if energy is in excess, BG can start to rise. On the contrary, reducing dietary fat alleviates lipotoxicity, increasing insulin sensitivity. This is why any diet which is calorie restricted, independent of macronutrient composition, produces weight loss and improves glucoregulation. Calorie restriction, by producing a calorie deficit, alleviates both gluco- and lipotoxicity. 

One of the important aspects for dealing with this subject is the fact that glucose intolerance can have many underlying causes. In this manner, a person with autoimmune diabetes may not tolerate carbohydrates as well as a person with only mild PaIR. The fact that PaIR may progress into beta-cell dysfunction (20, 21) can alterate the response to a high carbohydrate diet, and depending on the severity, extreme measures must be taken to achieve normal BG and insulin levels (such as severe calorie restriction). The distribution of body fat can also have consequences on glucoregulation (22). Last but not least, epigenetic changes produced in utero can affect glucose tolerance since the moment we are born (23). 

What is more important, in my opinion, is to address whether hyperinsulinemia causes or potentiates IR, or if hyperinsulinemia results from IR, by a compensatory mechanism. If the first hypothesis holds true, then a ketogenic diet would have an advantage over a low fat-high carbohydrate diet. Desensitization of target cells triggered by the same hormone (homologous desensitization) is a very common characteristic of hormone signaling. In short, high levels of a given hormone reduce the response of the cell to the hormone effects and a reduction in the level of this hormone resets sensitivity. Excess hormone signaling is harmful, so the cell's attempt to restore normality is mediated by reducing its response. This is exactly what happens with insulin: 

• Chronic hyperinsulinemia (in vivo and in vitro) causes a reduction in the number of receptors per cell and glucose transport (24, 25).
• Pre-incubation of 3T3-L1 adipocytes with high levels of insulin and glucose increase PTEN activity, which is correlated with decreased PtdIns(3,4,5)P3 (26). This metabolite is very important for intracellular signaling transduction of insulin.
• Hyperinsulinemia has shown to induce insulin resistance in humans (27).
• Overall, hyperinsulinemia is proposed to be a result and a driver of insulin resistance (28).

Obesity seems to be characterized by an increased amount of insulin being secreted, compared to lean subjects (29). So, while calorie restriction per se is responsible for improved glucoregulation, there might be a short-term benefit in consuming a high-fat ketogenic diet in T2DM and MetSyn patients. As the bodyfat mass and associated hormones regulate, the differences between hypocaloric diets with different macronutrient profiles might be eliminated. This seems reasonable for diet-induced insulin resistance, but not for autoimmune or severe diet-induced glucose intolerance. There seems to be a threshold in which many people cant fully recover their insulin sensitivity with dietary measures. This is where a more integrative and previously uncharacterized approach kicks in (this is the subject of my future post). 

Glucose and cancer

Glucose restriction for cancer treatment seems reasonable given the evidence on the dependence of most types of cancer on glucose for cell growth and proliferation. Unfortunately, the picture is not that simple (30). Although restricting glucose is a good idea, specially for glucose-dependent tumors, the evidence shows that cancer cells also feed on glutamine. More surprinsingly, some types of cancer can grow on fatty acids (31). Restricting glucose reduces insulin levels, which promotes cancer growth. Nevertheless, ideal levels of blood glucose and insulin for treating cancer can only be achieved via calorie restriction. In fact, many supporters of ketogenic diets for cancer often cite the study of Zuccoli et al (32) on the management of glioblastoma. But very few mention what is stated in the study:

"Due to the hyperuricemia the patient was gradually shifted to a calorie restricted non-ketogenic diet, which also delivered a total of about 600 kcal/day. This diet maintained low blood glucose levels and slightly elevated (++) urine ketone levels due to the low calorie content of the diet."

Despite switching to a non-ketogenic (by definition) diet, the patient still showed progress. In my opinion, besides glucose and protein restriction, calorie restriction (and probably fasting) is the dominant factor for achieving success during cancer treatment. 

Summary and key points

• Both energy substrates (glucose and fatty acids) support their own oxidation and inhibit the metabolism of the other.
• A diet high in fat and low in carbohydrates will reduce glucose metabolism and increase fat metabolism. Conversely, a high carbohydrate-low fat diet increases glucose utilization and decreases fatty acid metabolism.
• Increased glucose utilization implies upregulation of glucose membrane transporters and enzymes involved in glycolysis. Additionally, it reduces the activity of enzymes involved in fat metabolism. 
• Increased fatty acid metabolism inhibits key glycolytic enzymes, as well as GLUT membrane translocation. It also interrupts glucose/insulin signaling and stimulates lipolytic enzymes. 
• Chronic hyperinsulinemia, caused by peripheral insulin resistance and energy excess, aggraviates glucose intolerance. Both high glucose and high FFA levels promote this state, by different mechanisms. 
• Under energy balance, a high fat ketogenic diet might produce muscular insulin resistance, reducing glucose tolerance. This should not be compensated by an increase in blood glucose levels. However, if energy intake exceeds calorie expenditure and/or the body utilizes predominantely FFA for energy for extendend periods of time, there can be a rise in blood glucose to non-pathological levels. This is specially relevant if there is little exercise being done (exercise promotes muscular insulin sensitivity) and/or there is an abnormal condition.
• The etiology of glucose intolerance is very important for the proper treatment. Although calorie restriction is the primary solution for obesity/diet-induced insulin resistance, people with autoimmune (both congenital/perinatal or diet-induced)  and beta cell dysfunction should adopt a very low carb approach. 

In the end, the level of carbohydrates proposed by the Jaminet's is in the safe side. The alarmism promoted by some people is not supported. While severely restricting carbohydrates is, in my opinion, the best approach for MetSyn and obesity, once fat mass has reduced, one can tolerate more carbohydrate without problems. If the choice is restricting carbohydrates for life, you should expect a very abnormal response to any carbohydrate (being "safe" or "unsafe"). Nevertheless, lets not forget that the Perfect Health Diet is not a high carbohydrate diet, but a high-fat, low carbohydrate diet. Despite my obvious differences with Paul (33), his dietary advise is very reasonable and his diet is the first I recommend. This template, plus calorie restriction and/or fasting, is the best dietary measure one can implement. Everyone should adjust their individual carbohydrate needs, but in the end, the key is controlling and preventing inflammation. And carbohydrates per se are not inflammatory. 


*Certainly, there are people who are in the extremes of the Gaussian distribution. For these persons, extra measures should be taken. I will write about my approach in the following post. 

No time except for...

...finishing my project. I have to present a draft of my thesis research on January 16th, so I dont have much time to read any paper not related to it.

After that, hopefully I will be able to finish a few pending posts. 

Happy holidays!

Getting fat: the type matters

Traditionally, increased fat mass has been viewed as unhealthy irrespective of the distribution of body fat. With increasing research on the subject, most researchers agree that increased visceral adipose tissue (VAT) is the main determinant of the metabolic disorders associated with obesity, compared to increased subcutaneous adipose tissue (SAT). 

In the last months, there has been a not-so-scientific debate on whether being fat eating a "healthy" diet is better than being thin eating a Western diet. One can be healthy even with an increased body fat mass? Is gaining fat with a given diet different than with another diet?

A study done by Tran et al. (1) caught my attention and motivated me to dig a little further in this topic. The authors found that transplantation of SAT and VAT to the subcutaneous or visceral regions of recipient mice produced remarkable differences on glucose homeostasis, weight and body fat gain. The scheme utilized for the transplants is shown below:

Copyright © 2008 Elsevier Inc. All rights reserved.

The most important effect was noticed in SC-VIS mice, which were transplanted with SAT into the visceral cavity. Compared to other mice, the rate of body weight gain (fat was transplanted "on top" of endogenous adipose tissue) was significantly lower, gaining on average only 63% and 59% (they used two cohorts) of the amount gained by sham-mice at the end of the study. This was irrespective of calorie intake, energy expenditure or heat production. Basal plasma glucose levels were reduced by 15% and plasma insulin levels were reduced by 33% in SC-VIS mice. Compared to sham, SC-VIS mice had 70% lower plasma leptin levels, but adiponectin was also decreased. Intraperitoneal glucose tolerance tests showed that SC-VIS mice had the lowest glucose levels, and insulin sensitivity (assessed by hyperinsulinemic-euglycemic clamp) was higher in this group. Glucose uptake in endogenous SAT was increased in both groups of mice transplanted with SAT, reflecting an increase in insulin sensitivity. Finally, gene expression of adiponectin, resistin and leptin levels were decreased in SC-VIS mice, compared to sham. 

Overall, the study findings were:

• Transplantation of SAT into the visceral cavity produced the most significant results in terms of weight gain, glucose tolerance and adipocytokine levels.
• SC-VIS mice had decreased body weight, decreased body fat percentage, increased percent of lean mass, without significant changes in total energy expenditure or heat production.
• Transplantation of SAT into recipient mice improved insulin sensitivity in the liver and in endogenous SAT. 
• Transplantation of SAT into the visceral cavity decreased average adipocyte area by 38% compared to endogenous SAT, and did not increase the adipocyte's size to that of the endogenous VAT. 
• Adding SAT to the visceral cavity reduced mRNA levels of resistin, leptin and adiponectin, compared to endogenous SAT.

These results suggest a "protective" role of SAT in obesity. There is evidence that insulin resistance correlates with VAT, regardless of bodyweight (2). VAT appears to produce more IL-6 than SAT (3), which correlates with increased macrophage infiltration in VAT compared to SAT (4). Liposuction, despite reducing bodyfat levels, does not improve metabolic markers in the short and long term (5), does not improve insulin sensitivity of muscle, liver or adipose tissue; and doesn't affect levels of C-reactive protein, IL-6, TNFa and adiponectin in diabetic or normal subjects (6). Accordingly, SAT seems to modulate TNFa expression in VAT (7). 

Thus, it seems that it is not weight lost per se which is important for preventing metabolic damage, but the type of body fat lost. Liposuction achieves equal or greater weight loss than lifestyle modifications, but fails to improve metabolic parameters. 

Effect of different diets on body fat distribution

From the above discussion, it is reasonable to think that the best diet is the one that a. decreases body fat mass and b. reduces and/or redistributes fat mass towards SAT.

Active rats fed a ketogenic diet show increased SAT compared to matched carbohydrate-fed rats (8), despite similar body fat levels, although there are contradictory results (9). Weight loss produced either by a high fat-low carbohydrate diet or a low fat-high carbohydrate diet show the same effects on both SAT and VAT (10), suggesting that the macronutrient ratio is not important. This contrasts with a small study which showed that the visceral to subcutaneous fat ratio (V/S) decreased only in the low carbohydrate group (11), compared with the group eating a high carbohydrate diet, even when both diets were hypocaloric. Other authors suggest that ketogenic diets decrease VAT more significantly than high carbohydrate diets (12), although the method used to estimate VAT levels (DEXA) has some predictive problems (13). 

Chaston and Dixon (14) have proposed that acute caloric restriction produces a preferential loss of VAT in the short term and that this effect is seen with modest weight loss. Alternate day fasting (ADF) has also shown to improve body fat distribution in mice, increasing the proportion of SAT vs. VAT and levels of adiponectin, and reducing the levels of leptin and resistin (15, 16). These effects seem to be independent of the diet and body fat loss.

Summing up

Independent of total body fat, there seems to be a protective effect of SAT vs. VAT. This might be the reason why not all obese people develop metabolic syndrome or insulin resistance (17), as healthy obese subjects seem to have less risk for complications than normal-weight subjects with metabolic syndrome (18). Calorie restriction seems to be the most important factor for preventing an increase in VAT, while ADF might provide an additional benefit without weight loss. From the above, we can try to answer the questions proposed: 

One can be healthy even with an increased body fat mass? 

Yes, given a proper body fat distribution (higher proportion of SAT vs. VAT).

Is gaining fat with a given diet different than with another diet?

Possibly. Overfeeding studies done do not control for macronutrient composition, so there is no evidence of a different effect of different diets. However, from the studies available, gaining body fat while implementing ADF might be different than with a Western diet. Moreover, specific nutrients might have different effects regardless of body fat gain, such as fructose (19), although recent evidence do not show adverse effects of overfeeding fructose on visceral fat (20). In either case, having a normal-weight is not protective for cardiometabolic abnormalities (21). This suggests that dietary habits are important even in the absence of weight gain (normal-weight obesity), and that gaining weight with a healthy diet might not be as detrimental as gaining weight with a Western diet.

Tran TT, Yamamoto Y, Gesta S, & Kahn CR (2008). Beneficial effects of subcutaneous fat transplantation on metabolism. Cell metabolism, 7 (5), 410-20 PMID: 18460332