Nutrition & Metabolism - Latest Comments

Erratum

Didier Chapelot — 2012-07-16T16:10:46Z

Please note that a reference has been forgotten and wrongly attributed. This is reference [28] in the discussion section (last paragraph). The correct reference is "Lu CL, Zou X, Orr WC, Chen JD: Postprandial changes of sympathovagal balance measured by heart rate variability. Dig Dis Sci 1999, 44:857-861".
Moreover, the symbols of conditions in the figures are not stipulated. So, note that black squares indicate the exercise condition and white squares the rest condition.
Sorry for these errors.

Complex effects of D-lactate

Heikki Savolainen — 2012-07-04T16:43:59Z

Dear Editor,

Ling et al. (1) show convincingly that highly oxygen-depedent organs are more prone to the toxic effects of D-lactate than liver.

However, dosing of D-lactate in a liver cell culture has other very interesting effects. Namely, the PI3K/AktPKB/PKC acitivity is decreased which leads to low BAD activity allowing increased apoptosis (2).

This indicates that D-lactate can also have other significant metabolic effects e.g. in diabetics who have increased D-lactate burden because of excessive methylglyoxal from glucose (3).

1 Ling et al. Nutrition and Metab 2012; 9: 6

2 Miyamato. J Am Coll Surg 2007; 204: 182

3 Talasniemi et al. Clin Biochem 2008; 41: 1099

Typing error in Flatulence mean figures

Beatriz Sarria; — 2012-07-04T16:43:26Z

In table 7, under Flatulence, the mean figures are incorrect: instead of 2.14a of 2.07a and 2.32a they should read 1.42 a, 1.61a and 1.70a, respectively. The p value shown (0.019) corresponds to the correct set of data.

2012 follow-up of case?

Hans Krause — 2012-07-04T16:42:32Z

It would be interesting to know the follow-up on this case, now 2 years later. How has the patient fared since this article was written?

KD diet composition

Jeff Kiefer — 2011-06-21T17:57:09Z

I can't help but to think that the results may be more impressive if not based on the formulated diet that was used in this study. Crisco is anything but a natural and healthy oil and would compromise a number of confounding variables. Something such as a more natural sat. fat source, say coconut oil might be preferable. Additionally, it would certainly be more ketogenic. Think long term such supplementation in human subjects would be preferable to crisco.

CYP1A2*1F is not a 'rapid metabolizer' phenotype

Vidya Perera — 2011-06-21T17:55:13Z

The authors of this study conclude that bone mineral density (BMD) was lower in people who reported having high coffee consumption and also had rapid metabolism of caffeine (defined as having a particular CYP1A2 genotype), indicating `this group' of coffee consumers might be at special risk of bone loss and its associated clinical consequences. However, it is our view that this study does not take into account two critical factors related to CYP1A2 activity that influence the conclusions drawn. Firstly, the CYP1A2 polymorphism (-163 C>A) is associated with higher inducibility only in people who are cigarette smokers and secondly, environmental factors play a major and significant role in determining CYP1A2 activity.

Hallstrom et al., state that `The C allele at position -163 in the CYP1A2 gene is considered to confer decreased inducibility to the enzyme. Consequently, carriers of a C allele at this position are regarded as 'slow' metabolizers of caffeine'. Numerous studies have demonstrated that this allele (known as CYP1A2*1F) has no association with activity. It is associated with increased induction of CYP1A2 metabolic activity in people who are smokers (when compared to smokers who do not carry this allelic variation) but has no association with activity in non-smokers [2-4]. Furthermore, Hallstrom et al. have not determined CYP1A2 activity in individual subjects by phenotyping but have inferred activity from CYP1A2 genotype. Unlike other drug metabolizing enzymes, such as CYP2D6, where genetic polymorphisms are known to result in rapid and poor metabolizers, no such genotype-phenotype relationship has been demonstrated for CYP1A2 [5]. In contrast to CYP2D6, CYP1A2 is highly inducible by environmental factors. Previous studies have demonstrated that cigarette smoking, ingesting char-grilled meats and the use of oral contraceptives in females result in significant changes in CYP1A2 activity [6]. Interestingly, a recent study by Browning et al., has demonstrated that variability in the CYP1A2 gene is greater than first thought [7]. A number of simple assays and phenotyping protocols are available to measure CYP1A2 activity [8, 9].
The authors also state that `men who were high consumers of coffee' (defined as more than 4 cups of coffee a day) with `rapid metabolism of caffeine' had lower BMD. A recent study by Djordevic et al., demonstrated that heavy coffee consumption (defined as 3 or more cups of coffee a day) induced CYP1A2 activity suggesting that caffeine induces its own metabolism. Therefore, this subset of the population may be considered `rapid metabolizers' due to the possible induction of CYP1A2 by heavy caffeine consumption. However, this should be confirmed through CYP1A2 phenotyping.

In conclusion, both genetic and environmental factors play an important role in influencing CYP1A2 activity and should be accounted for in studies linking CYP1A2 activity to health conditions or outcomes using CYP1A2 phenotyping.

References

1 Hallstrom H, Melhus H, Glynn A, Lind L, Ann-Christine S, Michaelsson K (2010) Coffee Consumption and CYP1A2 Genotype in Relation to Bone Mineral Density of the Proximal Femur in Elderly Men and Women: A Cohort Study. Nutrition & Metabolism 7 (1): 12

2 Aklillu E, Carrillo JA, Makonnen E, Hellman K, Pitarque M, Bertilsson L, Ingelman-Sundberg M (2003) Genetic polymorphism of CYP1A2 in Ethiopians affecting induction and expression: characterization of novel haplotypes with single-nucleotide polymorphisms in intron 1. Mol Pharmacol 64 (3): 659-669

3 Ghotbi R, Christensen M, Roh H-K, Ingelman-Sundberg M, Aklillu E, Bertilsson L (2007) Comparisons of CYP1A2 genetic polymorphisms, enzyme activity and the genotype-phenotype relationship in Swedes and Koreans. Eur J Clin Pharmacol 63 (6): 537-546

4 Sachse C, Bhambra U, Smith G, Lightfoot TJ, Barrett JH, Scollay J, Garner RC, Boobis AR, Wolf CR, Gooderham NJ, Colorectal Cancer Study G (2003) Polymorphisms in the cytochrome P450 CYP1A2 gene (CYP1A2) in colorectal cancer patients and controls: allele frequencies, linkage disequilibrium and influence on caffeine metabolism. British Journal of Clinical Pharmacology 55 (1): 68-76

5 Ingelman-Sundberg M, Sim SC, Gomez A, Rodrigues AD (2007) Influence of cytochrome P450 polymorphisms on drug therapies: Pharmacogenetic, pharmacoepigenetic and clinical aspects. Pharmacology & Therapeutics 116: 496-526

6 Le Marchand L, Franke AA, Custer L, Wilkens LR, Cooney RV (1997) Lifestyle and nutritional correlates of cytochrome CYP1A2 activity: inverse associations with plasma lutein and alpha-tocopherol. Pharmacogenetics 7 (1): 11-19

7 Browning SL, Tarekegn A, Bekele E, Bradman N, Thomas MG (2010) CYP1A2 is more variable than previously thought: a genomic biography of the gene behind the human drug-metabolizing enzyme. Pharmacogenetics and Genomics 20 (11): 647-664

8 Perera V, McLachlan AJ, Gross AS (2010) Caffeine and paraxanthine HPLC assay for CYP1A2 phenotype assessment using saliva and plasma. Biomed Chromatogr 24 (10): 1136-1144

9 Perera V, McLachlan AJ, Gross AS (2010) Pharmacokinetics of Caffeine and Paraxanthine in Plasma and Saliva in Healthy Volunteers. In Preparation

Error correction of genotype name in Table 2 and Table 3

Oh Yoen Kim — 2011-06-21T17:53:06Z

"FEN1-10154G>T " was duplicated In Table 2 and Table 3. The second one should be changed to "FADS3 rs1000778"

[ Table 2 ]
second "FEN1-10154G>T " [GG (n=259), GT+TT (n=308)] should be changed to FADS3 rs1000778 [CC (n=280), CT+TT(n=287)]

[ Table 3 ]
second "FEN1-10154G>T " [GG (n=259), GT+TT (n=308)] should be changed to FADS3 rs1000778 [CC (n=280), C carrier (n=287)]

Protein and ageing

eric anderson — 2011-01-26T12:03:48Z

I would like to see a folow up to look at protein levels of 6.25, 7.5, 8.75 and 16% of calories from protein on older pigs (75% of average lifespan) to see the effect of the change in diet and the pig longevity.

I believe you mean

Laura Buti — 2011-01-26T12:00:58Z

(from page 2)
"Whey proteins also modulate several hormones that influence body
composition. Short term acute studies with whey proteins corroborate
the body composition changes seen with longer term feeding studies.
Whey protein isolate (75 grams per dose) was evaluated [12] for its
impact on obesity-related hormones in an acute (5 hour) protein
ingestion in overweight and obese women with polycystic ovary syndrome
(PCOS). The acute hormonal response showed significantly lower
hyperinsulinemia (less lipogenesis), lower cortisol levels (lean
muscle preservation) and increased ghrelin release (satiety
enhancement)."

The last line in the paragraph is inaccurate, as even the most amateur
nutrition student can tell you. Increased ghrelin release stimulates
appetite, not satiety. Satiety is enhanced by the release of the
hormone known as leptin, and is released after a meal to let the body
know it's had enough. A quick reference to research cited earlier
in the paragraph also indicates the link between ghrelin and hunger,
and suggests that the acute hormonal response to the whey supplement
resulted in the suppression of ghrelin, not the increased release of
the hormone.

In addition to this inaccurate review of the published material, in
the methods section of the same article, diet "dairies" are discussed,
rather than diaries. Thought you'd like to correct the simple typo.

Diet-Induced Thermogenesis

Frank Dobner — 2010-07-02T16:57:52Z

I have thought about thermogenesis many times since I first learned about it. Not being a medical practitioner, I have a question about this I would like pose.

Many people of the world are being encouraged to eat smaller and few meals on the basis that it will encourage diet-induced thermogenesis. However, if this thermogenesis is a function of simply how much is eaten in a day, why would it matter if you ate once or six times?

Your contribution to this question would be very appreciated.

Frank Dobner
Male Weight Loss Now