Goi's Fitness Forum

Finally, the most intriguing finding was that although the KO mice were leaner, food intake was much greater (up to 18% more caloric intake) with a normal fat absorption [85], raising the question: Where does all this energy go? How does the lack of ASP result in repartitioning and disposal of excess energy? The balance of body energetics would predict that any calories ingested, and not stored in some form, would have to be expended as energy. The major options are increased activity or enhanced thermogenesis. Preliminary results presented at a recent meeting (late breaking abstract, NAASO 2001) demonstrated increased oxygen consumption in KO mice, but no changes in overall activity, suggesting alternate disposal routes in the absence of efficient adipose tissue storage.

With the many factors that change postprandially or in insulin-resistant states such as diabetes, it is difficult to pinpoint exactly which component might be responsible for the stimulation of C3 and ASP production. Experiments with cultured human adipocytes have demonstrated that insulin (to a moderate degree), but especially chylomicrons, appear to stimulate both C3 and ASP production [44, 45 and 46]. On the other hand, Koistinen et al. [39] showed that a euglycemic (4 h) hyperinsulinemic clamp had no effect on C3 mRNA levels. C3 mRNA did correlate with BMI, glucose disposal rate, plasma triglyceride, non-esterified fatty acid (NEFA) and leptin (n=12 subjects) [39]. We speculate, therefore, that ASP production may be up-regulated in insulin-resistant states, perhaps by one of the factors listed above.

A recent article demonstrated that diets containing differing types of fat (polyunsaturated vs. trans fatty acids) have been shown to influence fasting ASP levels after several weeks feeding in hypercholesterolemic women [47].

• 1. Down regulation of the gene expression that regulates ASP production results in an organism consuming and expanding more calories than it normally should at the expense of accumulating fat.
  2. Diet influences ASP production.

Recent evidence in knockout (KO) ASP deficient (C3 KO) and C5L2 knockout (C5L2 KO) mice studies highlight the role of ASP and its receptor C5L2 as a peripheral gatekeeper. As C3 is the precursor to ASP, C3 KO mice are obligate ASP deficient. Initial studies [41] and [42] clearly demonstrated that the absence of ASP led to postprandial lipemia, while acute ASP injection normalized the response. Factor B KO mice, which have circulating C3 but under normal unstressed conditions have no circulating ASP, also demonstrate a similar profile [43]. Interestingly, the absence of ASP also leads to a reduction in storage within adipose tissue. The recent identification of C5L2 as a receptor for ASP [30] and [31], and the acquisition of C5L2 KO mice, has permitted further confirmation. C5L2 KO mice demonstrate similar delays in postprandial TG and NEFA clearance, with a marked reduction in ex vivo adipose tissue lipogenesis, absence of ASP stimulation and increased basal lipolysis [44]. Notwithstanding the apparent decrease in adipose storage, all KO models examined (C3 KO, factor B KO, C5L2 KO and ob/ob C3(−/−) double KO) demonstrate mild or marked hyperphagia [41], [42], [44], [45], [46] and [47].

Lipid flux, and thus LPL, is controlled by events within the adipocyte. In the absence of ASP, where does the energy go? ASP deficient mice and C5L2 KO mice have increased basal and food-induced thermogenesis, as well as mild to marked increase in physical activity in ASP KO mice [44] and [45] Z. Xia, K.L. Stanhope and E. Digitale et al., Acylation-stimulating protein (ASP)/complement C3adesArg deficiency results in increased energy expenditure in mice, J Biol Chem 279 (2004), pp. 4051–4057. View Record in Scopus | Cited By in Scopus (24)[45]. In fact, this increase in energy expenditure can partially reverse the decreased energy expenditure and insulin resistance associated with leptin deficiency [46]. Brown adipose tissue does not appear to contribute to the increased energy expenditure [45]. Interestingly, there is increased flux of NEFA to muscle and liver, with increased lipid oxidation, and overall increases in energy expenditure as compensation. Recent data indicates that this up-regulation is due to increased mitochondrial activity reflected by increased markers including CD36 and cytochrome C [47]. As C5L2 is also expressed in muscle and liver, whether this effect is a direct consequence of the absence of ASP or the result of increased fatty acid fluxes remains to be determined.

In preadipocytes, insulin and dexamethasone increased C5L2 mRNA (1 micromol/L insulin resulted in a 2.6-fold increase...

Plasma acylation stimulating protein, adipsin and lipids in non-obese and obese populations*.

Articles
European Journal of Clinical Investigation. 29(8):679-686, August 1999.
Maslowska, M. *; Vu, H. *; Phelis, S. *; Sniderman, A. D. *; Rhode, B. M. +; Blank, D. +; Cianflone, K. *

Abstract:
Background: Acylation stimulating protein (ASP) is a potent stimulator of TG synthesis in human adipocytes.

Design: In the present study, we have analysed plasma ASP and adipsin levels and their relationships to plasma lipids in non-obese and obese groups.

Results: The results show that the frequency distribution of ASP is skewed but that of adipsin is normal in both groups. In the non-obese population, the mean levels of plasma ASP and adipsin were 20.2 nmol L-1 (median) and 66.6 +/- 19 nmol L-1 (mean) respectively. No difference was observed between men and women for each of the parameters. In the obese population, the median plasma ASP was increased by 246% (69.9 nmol L-1) and adipsin by 31% (87.0 +/- 22.7 nmol L-1) above that of the control group. Although the levels for men and women were not statistically different for adipsin, the median ASP plasma concentration was 1.9-fold higher in obese women than in obese men (71.8 nmol L-1 vs. 37.6 nmol L-1, P < 0.05). Best subset regression analysis provided a model with variables that best predict plasma ASP [r2 = 0.160, P < 0.008 for body mass index (BMI), P < 0.05 for triacylglycerol (TG), P < 0.03 for free fatty acid (FFA)] and plasma adipsin (r2 = 0.057, P < 0.017 for BMI) in a non-obese population. In obese subjects, the model was different for plasma ASP (P = NS for any of the variables) and plasma adipsin (r2 = 0.356, P < 0.008 for FFA, P < 0.0002 for BMI, P < 0.02 for age). There was no correlation between ASP and adipsin in either the non-obese or the obese group.

Conclusion: The present data suggest involvement of the ASP/adipsin pathway in the pathogenesis of obesity.

The effects of acylation-stimulating protein (ASP) and insulin on free fatty acid (FFA) release from isolated human fat cells and the signal transduction pathways to induce these effects were studied. ASP and insulin inhibited basal and norepinephrine-induced FFA release by stimulating fractional FFA re-esterification (both to the same extent) and by inhibiting FFA produced during lipolysis (ASP to a lesser extent than insulin). Protein kinase C inhibition influenced none of the effects of ASP or insulin. Phosphatidylinositol 3-kinase inhibition counteracted the effects of insulin but not of ASP. Phosphodiesterase 3 (PDE3) activity was stimulated by ASP and insulin, whereas PDE4 activity was slightly increased by ASP only. Selective PDE3 inhibition reversed the effects of both ASP and insulin on fractional FFA re-esterification and lipolysis. Selective PDE4 inhibition slightly counteracted the ASP but not the effect of insulin on fractional FFA re-esterification and did not prevent the action of ASP or insulin on lipolysis. Thus, ASP and insulin play a major role in regulating FFA release from fat cells as follows: insulin by stimulating fractional FFA re-esterification and inhibiting lipolysis and ASP mainly by stimulating fractional FFA re-esterification. For both ASP and insulin these effects on FFA release are mediated by PDE3, and for ASP PDE4 might also be involved. The signaling pathway preceding PDE is not known for ASP but involves phosphatidylinositol 3-kinase for insulin.

Abstract Acylation stimulating protein (ASP) is a 14 kDa plasma protein which causesin vitro triacylglycerol synthesis in human adipocytes and fibroblasts to increase substantially. ASP was found to stimulate human adipose tissue microsomal glycerophosphate acyltransferase and diacylglycerol acyltransferase activities by 23% and 90%, respectively. However, phosphatidate phosphohydrolase activity showed no increase in activity, nor did microsomal acyl-CoA synthetase activity. Moreover, ASP did not decrease the apparent Km of diacylglycerol acyltransferase (DGAT), but rather increased its apparent Vmax suggesting direct interaction of ASP with DGAT.

J Beaty: What are your thoughts on the reemergence of the macronutrient food combining theory where carbs shouldn't be mixed with protein/fat meals and fat shouldn't be mixed with protein/carb meals?

L Norton: This is a rather simplistic way of looking at nutrition and focuses mainly on insulin rather than looking at the whole picture. While it probably isn't a good idea to have a really high carb meal with a really high fat meal, there's nothing wrong with having moderate amounts of both.

W Brink: like many theories, it comes around every few years or decades and gets people all worked up over their food. Problem is, it's no more true today then it was when the book Fit for Life by Harvey and Marilyn Diamond came out. The theory had no scientific support then and it has none now. Humans have been combining fats, carbs, and proteins quite successfully for eons and as omnivores, are perfectly capable of digesting mixed meals.

J Hale: You are probably referring to the theory that assumes insulin and blood levels of fat should never be raised at the same time. This theory assumes that insulin is the key contributor to obesity. There are a few things wrong with this line of thought. One of the key problems is not recognizing something called Acylation Stimulating Protein. Acylation stimulating protein (ASP) is a hormone produced by adipocytes and is of importance for the storage of energy as fat. The consumption of dietary fat alone can increase fat storage. Dietary fat affects fat cell metabolism with NO INCREASE in insulin. Some studies have indicated dietary fat loading found a decrease in HSL (hormone sensitive lipase) and an activation of fat storage despite no increase in insulin. The key reason was activation of acylation stimulating protein (ASP) which is activated by the presence of chylomicrons (basically packaged triglycerides that are found in the bloodstream after the meal). ASP increases glucose uptake into the fat cell, increases insulin release from the pancreas and has been described as 'the most potent stimulator of triglyceride storage' in the fat cells by numerous scientists. Another problem with this line of thought is some proteins causes substantial elevations in insulin. Minimal levels of insulin affect fat cell metabolism. Basal levels can decrease lipolysis by 50%. Another consideration is most bbers are eating every 2-3 hrs so nutrients are still absorbing from previous meals; therefore previous meals interact with the blood levels of nutrients of the present meal.

A study conducted by Golay and colleagues compared a diet with equal macronutrient content and substrate percentages; that differed only in how the substrates were consumed (mixed diet vs. food combining). The results were no difference in weight loss. Here are the exact results reported by the researchers. “Results: There was no significant difference in the amount of weight loss in response to dissociated (6.2 +/- 0.6 kg) or balanced (7.5 +/- 0.4 kg) diets. Furthermore, significant decreases in total body fat and waist-to-hip circumference ratio were seen in both groups, and the magnitude of the changes did not vary as a function of the diet composition. Fasting plasma glucose, insulin, total cholesterol and triacylglycerol concentrations decreased significantly and similarly in patients receiving both diets. Both systolic and diastolic blood pressure values decreased significantly in patients eating balanced diets. The results of this study show that both diets achieved similar weight loss. Total fat weight loss was higher in balanced diets, although differences did not reach statistical significance. Total lean body mass was identically spared in both groups. CONCLUSION: In summary at identical energy intake and similar substrate composition, the dissociated (or 'food combining') diet did not bring any additional loss in weight and body fat”. Actually looks like a slight increase in fat loss with mixed diet (balanced diet). We have tons of anecdotal evidence that denies the need for food combining. We have evolved on a mixed diet. With all of that said food combining may be beneficial regarding calorie control. Once you eliminate an entire macronutrient from a meal this can go a long way in decreasing total caloric intake. If this is what you need to do to control energy intake feel free to do so.

A Aragon: I think that the “P+C & P+F = okay but avoid C+F” principle is idiotic when applied across the board without any contingencies or attention to individual situations. For example, if someone is low-carbing for whatever reason you choose (pathological carbophobia included), they might be done with their carb intake by early afternoon, and their meal construction for the rest of the day is gonna be primarily P+F by sheer default. In the latter scenario, I can see the principle being legit. However, when issued blanketly, it’s usually based upon the wacky idea that you don’t want fat floating around systemically when your insulin levels are high, because this will magically shift your net adipose balance in the positive. That’s false for a number of reasons. First of all, the insulin response generated by CHO + fat generally depends upon the degree of the fat’s saturation. Unsaturated fats tend to either lower insulin response of the coingested carbs, or not affect insulin response at all. Coingested sat fat, on the other hand, tends to raise insulin response, and can do so in a synergistic fashion. But then the question becomes, so what? Others have mentioned the more direct role ASP has in TG synthesis, and indeed, insulin is more of a multi-tasking anabolic/anticatabolic agent in comparison to ASP, which seems to exist solely to pump up the adipocytes. And of course the kicker is that ASP can do its TG-synthesizing magic in the sheer absence of insulin.

And then there’s energy balance… In a negative energy balance, insulinogenesis is wonderful thing, as long as the training stimulus & nutrition is there to work in concert with it to preserve LBM. In the condition of a positive energy balance, trainees in general are gonna have a lot more carbs to throw around, so this makes the whole separation thing even more dicey. Which meals should be carb-free or fat-free in order to pull of this magic separation tactic, and why? The logical answers to this question simply don’t exist. If you were to actually adhere to the mechanics of separation, you’d actually be hard-pressed to maintain a stable insulin profile – which is ironic, since the control of insulin is what “separatists” are aiming for. Regardless of all the previous points, the fundamental shortsight is that digestion/absorption of meals overlap each other when meal frequency is as high as it should be. Therefore, attempting strict separation of the macros = kidding yourself. Not to mention, most foods in nature are a combo of all the macros to begin with.