Calorie Restriction in Nonhuman Primates: Implications for Age-Related Disease Risk

Summary: Calorie restriction (CR) probably reduces diabetes and heart disease markers in rhesus monkeys. It also probably maintains DHEAS levels.

Interestingness: 3

Paper by Mark A Lane, Angela Black, Donald K Ingram and George S Roth in the Journal of Anti-Aging Medicine, Volume 1, Issue 4, Winter 1998.

(((I had already read a follow up paper published in 2010, so I knew the movie continued to go relatively well, but not fantastically so. That detracted from the excitement. This paper focuses on the effects of CR on diabetes and cardiovascular disease, and by measuring biomarkers in the latter case. Mortality would have been more interesting, but most likely the numbers would have been too low at such an early stage of the study. In any case, since CR seems to be the only "easy" intervention to make a difference for now, it's still a relatively interesting read.)))

Calorie restriction (CR) (((lowering food calorie intake by about 30% while maintaining good nutrition))) extends lifespan in lots of short-lived species, including rotifers (((little water animals, about half a milimetre long))), water fleas (((same))), fish, spiders, hamsters, mice and rats. Doing the relevant controlled experiment in humans would be tricky and take a long time. Doing it on rhesus monkeys is a close approximation and until animal-liberationists bomb them, less problematic.

Four experiments are reviewed. Two proper long-term randomised control studies on groups of 200 and 80 monkeys, the first one (NIA) in its 12th year, starting on sets of 1-2 year olds, 3-5 year olds and of > 17 year old monkeys, and the second one (UW) on 8-14 year old monkeys (((lifespan of rhesus monkeys is around 40 years))). One of the others (BGWF) is a short term (4 years) study on the cardiovascular effects of CR on 32 8-year old crab-eating macaques, the study being in its second year. The final study (UMB) is on 8 weight-stabilised rhesus monkeys which by coincidence happened to have a food regime similar to CR monkeys.

From the NIA study, the following effects are seen on the monkeys:
Decreases in:

• Body weight


• Fat and lean mass


• Trunk to leg fat ratio


• Fasting glucose/insulin


• Metabolic rate (short term)


• Body temperature


• Triglycerides


• IGF-1/growth hormone


• IL-6


• Rate of decline of DHEAS


• Lymphocyte number

Increases in:

• Insulin sensitivity


• HDL_2B


• Time to sexual maturation


• Time to skeletal maturation (((table says opposite on these last two, but text is clearer)))

No changes in:

• Metabolic rate (long term)


• Locomotion


• Testosterone


• Estradiol, LH, FSH, Progesterone


• Wound closure rate


• Clonal proliferation


• Beta-galactidase senescent cells


• Lymphocyte calcium response

All of these agree with rodent CR studies, in the cases where the rodent data is available, except for the lymphocyte calcium response.

(((That could really do as a summary, but the paper had another eight pages to go)))

With regards to diabetes and glucose regulation, there is another handy table summarising all the studies:

Both big studies agree in all of the following results:

• Decrease in fasting glucose


• Decrease in fasting insulin


• Decrease in insulin response


• Increase in insulin sensitivity


• No increase in glucose tolerance

The small coincidental study disagrees with regards to fasting glucose and glucose tolerance, and the short term study with respect to fasting insulin.

The effect of CR on cardiovascular disease doesn't appear to be as clearly beneficial. While triglyceride levels decreased the effect on LDL, HDL and total cholesterol was not statistically significant. By analysing HDL fractions, an increase in HDL_2B levels was measured. In the female subset of monkeys, lower total cholesterol and blood pressure was measured in CR monkeys compared to control monkeys. Lower arterial stiffness was also measured in male CR monkeys.

(((A graph at the end shows lower rate of decline of DHEAS (dehydroepiandrosterone-sulfate) in male CR monkeys, which would probably be the most interesting part of the paper. The framing of the graph seems a bit too purposeful though (why only show 3 years between 6 and 9 years of age?) )))

Abstract follows:

Calorie restriction (CR)—undernutrition without malnutrition—ranks among the most reproducible and widely used research paradigms in gerontologic research. This intervention is the only manipulation that has been shown consistently to extend the life span, delay onset and slow tumor progression, and retard physiologic aging in many systems. A large body of literature exists documenting these remarkable effects in such diverse short-lived species as rotifers, water fleas, fish, spiders, hamsters, and laboratory mice and rats. However, it is not known if CR has similar effects in longer-lived species more closely related to humans. Two major studies in rhesus monkeys, one at the National Institute on Aging and the other at the University of Wisconsin, were begun several years ago to address this question. Two similar studies focusing mostly on disease end points such as obesity, diabetes, and cardiovascular disease are also underway at the University of Maryland and Bowman-Gray School of Medicine. These studies have clearly shown that most physiologic responses assessed in monkeys on CR parallel the extensive literature on rodents. This article focuses on data related to various risk factors for age-associated diseases, in particular diabetes and cardiovascular disease. Although it will be several more years before definitive results regarding life span are available, emerging data from the monkey studies strongly suggest that CR alters several disease risk factors and may affect postmaturational aging in some systems. Therefore, it is likely that this nutritional intervention will result in at least moderate increases in the primate life span related to amelioration of certain age-related diseases and their complications.

Immunosenescence: Analysis and Genetic Modulation of Replicative Senescence in T Cells

Summary: T-cell senescence might be an important part of aging.

Interestingness: 4

Paper by Rita B Effros and Hector F Valenzuela in the Journal of Anti-Aging Medicine, Volume 1, Issue 4, Winter 1998.

(((These people want to try out upregulating telomerase in old T-cells)))

A major part of the function of T- and B-lymphocytes is based on replication. When differentiating from hematopoietic stem cells, the molecules or particles which the future mature lymphocytes are sensitive to (aka antigens) are encoded by a few sequences of DNA which are combined in random fashion. This makes the system potentially sensitive to hundreds of millions of different antigens. When an antigen is bound by a lymphocyte, the lymphocyte starts replicating, making identical clones (ie their receptor which sensed the antigen is not modified). When the antigen is no longer found in the environment, most of the lymphocytes disappear, but a few memory lymphocytes with the particular receptor remain so that the system can be revved up faster the next time that specific antigen is in the system.

Senescent T-cells can be generated in vitro by repeatedly exposing them to interleukin-2 (IL-2), a T-cell specific growth factor. After about 25-40 replications, they become senescent (ie they stop replicating). Fibroblasts (connective tissue cells) also become senescent after about 21 replications.

The receptor CD28 is not expressed in 95% of CD8+ senescent T-cells, and in all CD4+ senescent T-cells. Without CD28 costimulation, antigen binding doesn't lead to cell replication. CD28 signal transduction upregulates IL-2. It is also hypothesised to upregulate telomerase activity. Telomerase is very active in lymphocytes under certain conditions: in developing T-cells in the thymus and in lymphoid organs, when stimulated with mitogens (particles that upregulate replication), or by combination of antibodies to CD3 and CD28. When CD28 binding is inhibited, telomerase remains inactive even if there is strong stimulation of its T-cell antigen receptor (TCR). Even though telomerase is sometimes active in T-cells, senescent T-cells have short telomeres typical of other senescent cells. When split into CD28+ and CD28- T-cells, CD28- cells have shorter telomeres and lower replicative capacity when stimulated.

In vivo, CD28- T-cells are 1% fraction of neonates' total T-cells, 30% of (average) 78 year olds, 40% of people over 100, and 50% of HIV patients. Telomere lengths also shorten in peripheral blood lymphocytes as age increases. This loss of CD28 and shortening of telomeres is more pronounced in CD8+ cells, which specialise in anti-viral and anti-tumor activity, than in CD4+ cells (((doesn't this contradict the earlier numbers of 95% in CD8 and all in CD4?))). This could be due to infections by viruses that do not disappear (eg Epstein-Barr, varicella) or by repeated infections (eg influenza).

As people age, memory T-cells become a larger fraction of all T-cells. Senescence is also more common among memory cells. Non-senescent T-cells in old people respond to activation as strongly as those in young people.

During normal immune system activity, once the antigen dissapears from the system, most T-cells die by apoptosis. Senescent cells respond to apoptotic signals much less strongly, especially among CD8+ cells. These leftovers memory T-cells could be crowding out the production of new more useful T-cells. In calorie restricted mice, apoptotic response is maintained at youthful levels.



Abstract follows:

Immunosenescence, which constitutes one of the most dramatic physiologic changes associated with aging, may account for the increased susceptibility to infections and the high incidence of cancer in the elderly. A novel facet of T-cell biology has been recently identified that may exert a considerable impact on immune control over infections and cancer during aging. Cell culture studies have shown that after repeated rounds of antigen-driven proliferation, T lymphocytes eventually reach replicative senescence, an irreversible nonproliferative state associated with the loss of expression of a critical T-cell signaling molecule. Identification of this unique, cell-specific marker of senescence has facilitated the documentation and analysis of replicative senescence within the immune system in vivo during aging. This article summarizes the features of T-cell replicative senescence and highlights several genetic strategies that may reverse the process. The ability to manipulate T-cell replicative senescence may ultimately provide a fresh therapeutic approach to extend the years of immunologie "coverage" in the elderly.

Rest of Volume 1, Issue 3

The rest of the third issue consists of a favorable review of a popular science book about aging by Ben Bova, a summary of a telomeres and telomerase conference, an overview of the Gordon conference on aging, a review of a paper on the reasons for longer female longevity compared to male longevity, and the usual literature and web watch.

The review of the paper on longer female longevity doesn't mention anything new (hypotheses: estrogen as protective substance, less risky behaviour, two X chromosomes acting as backup, blood loss through menstruation lowering iron load)

The Gordon conference is an interesting idea. People show unpublished material, with the condition that noone else is meant to publish about it. Because of this condition though, the overview was very high level.

Interesting bits from the telomerase conference:

• Three models of the link between telomeres and cell senescence: short telomeres trigger a DNA-damage response; proteins that bind to longer telomeres get released, regulate transcription somehow; the area around the telomeres are tightly bound and therefore those genes suppressed when the telomeres are long, so when they shorten they become active.
• 90% of all malignant tissue has active telomerase
• T cells replicated to exhaustion lack expression of CD28. T cells lacking expression of CD28 become increasingly prevalent in vivo during aging.

Circadian Hyper-Amplitude-Tension (CHAT): A Disease Risk Syndrome of Anti-Aging Medicine

Summary: Large circadian changes in blood pressure are possibly a very high risk factor for ischemic stroke. More data needed.

Interestingness: 2

Paper by Franz Halberg, Germaine Cornélissen, Julia Halberg, Henry Fink, Chen-Huan Chen, Kuniaki Otsuka, Yoshihiko Watanabe, Yuji Kumagai, Elena V. Syutkina, Terukazu Kawasaki, Keiko Uezono, Ziyan Zhao and Othild Schwartzkopff in the Journal of Anti-Aging Medicine, Volume 1, Issue 3, Fall 1998.

(((Back from hiatus. I found this paper more interesting than the usual, mainly because I hadn't heard about the topic before. Wikipedia calls the main author of this paper the founder of (American) chronobiology, and this paper seems to be part of the field. I'd never heard of it until now. The graph is full of what now would be considered retro-graphs which do help a lot)))

(((The language used in the paper is a bit salesmanish. It stresses two cases in which circadian hyper-amplitude-tension (CHAT) was diagnosed, with one case being treated, and the other not, and the large amount of money lost in treating the negative outcomes of the second case. I wouldn't be surprised if the field is considered quackish by academics)))

(((Switching back to paper mode))) The paper highlights the negative effects of having a high range (or double amplitude) (ie maximum value minus minimum value) in the smoothed measurements of blood pressure across the day. This is not about the difference between systolic and diastolic pressure but about comparing systolic vs systolic, or diastolic vs diastolic, throughout the day, and determining whether the differences are too high. The treatment recommended, briefly, consists of relaxation techniques and timed doses of anti-hypertension drugs.

To measure the double amplitude, a sine wave is fitted to the raw measurements which are taken across many days (((the more days the merrier it seems, but the ones mentioned seemed to fluctuate between 2 and 20 days))). (((least square error regression of the following formula:


(image taken from http://www.cbi.dongnocchi.it/glossary/Cosinor.html). The MESOR is the midline-estimating statistic of rhythm (some kind of mean), and the acrophase would be a phase adjustment. I think the MESOR, the amplitude, the period and the acrophase are fit simultaneously, but the period seems "seeded" to 24 hours))). Two separate curves are created, one for systolic and one for diastolic pressure. The MESOR is the value halfway between the peak and trough, and the double amplitude is the difference between the peak and trough of these curves. If the double amplitude measurement exceeds the 95th percentile for the person's particular age/gender bracket, that person is diagnosed with CHAT.

The main evidence presented as to the importance of CHAT is a study of 297 people who had their blood pressure monitored continuously for 48 hours, and then their incidence of negative vascular events recorded for six years (((Not sure what. Stroke and heart attacks I presume, but what else?))) The relative risks of the following conditions were calculated (Approximate 95% CI range in brackets):

• BMI > 25kg/m^2: 0.6 (0.2-2.1)
• High cholesterol: 1.0 (0.4-3)
• Male: 1.7 (0.55-4.8)
• Drinking: 2.5 (0.9-7.5)
• Family history: 2.6 (0.6-11)
• Smoking: 2.7 (1.0-8)
• Age > 60: 4.7 (1.6-12)
• Systolic MESOR > 130mmHg: 4.1 (1.0-16)
• Systolic CHAT: 6.2 (2.2-15)
• Diastolic CHAT: 8.2 (3-20)
  

(((The numbers of incidents were clearly quite low if the CI bars are so wide)))

Focusing on ischemic strokes, the relative risk of people with CHAT compared to people without CHAT are also much higher than 1.0 when partitioning the people into MESOR buckets, for every bucket, although in this case the CI ranges are even wider and include 1.0 in most cases. These high risk factors also remain when any of the other individual risk factors mentioned in the previous list are absent, and all with estimates higher than 5.0. Again, the ranges are big, but in this case, they do not touch 1.0.

Other studies cited are ones in which: 424 people that were measured for 24 hours, in which CHAT was related to higher left ventricular mass index; 18 11-14 year olds and the relation between CHAT and betamimetics received while in the womb; and a study of 40 rats in which CHAT preceded high MESOR by weeks.

Conclusion: More data would be nice to get so that the confidence interval ranges are tightened, and so that the findings don't feel like searching for the impressive statistic among a bunch of numbers. The relative risk values cited for stroke are impressive though. It could be a fun project over a week to check for CHAT.

Abstract follows:

Serial measurements, taken around the clock in the laboratory and clinic, can be analyzed by computer-implemented curve-fitting to assess the approximate 24-hour (circadian) variation, among other rhythmic and chaotic components of the time structure (chronome) of any variable. This approach is particularly important to quantify blood pressure variability, which renders even the most accurate single measurement into a snapshot on a roller coaster. A seemingly acceptable blood pressure can be particularly misleading when accompanied by the recommendation of another check-up in 2 years, which is the official position of the World Health Organization. An overswinging of the blood pressure along the 24-hour scale may then be missed. This excessive circadian amplitude, called "circadian hyper-amplitude-tension" (CHAT), constitutes a new disease risk syndrome, warranting screening, diagnosis, and treatment. With or without the midline-estimating statistic of rhythm (MESOR) (i.e., the [chronome-adjusted] mean value), the circadian double amplitude, a measure of the extent of predictable change within a day, is a predictor of vascular disease risk. An excessive amplitude (above the upper 95% prediction limit of healthy peers matched by age, gender, and ethnicity) is associated with an elevated left ventricular mass index in a retrospective chronometa-analysis of data from 424 patients and with an increase in morbid events in a prospective 6-year study on 297 patients, following-up on ancillary clinical studies and on results obtained on the laboratory model of the stroke-prone spontaneously hypertensive rat. CHAT is associated with a 720% increase in risk of ischemie cerebral events. It represents the greatest increase in risk, compared with 310%, 370%, 160%, 170%, and 150% in relation to a high blood pressure, old age, a family history of high blood pressure, and/or of other vascular disease, smoking and alcohol consumption, respectively. To identify CHAT and for other diagnostic and therapeutic reasons, single measurements should be replaced by an around-the-clock profile, for a week or longer, if need be, at the outset. The profile is preferably obtained by automatic monitoring with ambulatorily functional instrumentation. When such a monitor is unavailable, self-measurements at 3-hour intervals during waking and one around midsleep are acceptable. The midsleep measurement is taken with minimal disturbance, preferably by a companion, while the patient sleeps with a cuff on the arm. When no companion is available, the patient can set an alarm clock to take the self-measurement. Treatment should be timed with individualized guidance by a blood pressure profile (chronotherapy). The same profile also serves to assess the treatment effect with a control chart to validate the reduction of an excessive amplitude, the lowering of the blood pressure, or both when elevated. Controlled clinical trials assessing long-term outcomes are overdue. By monitoring for only weeks, the recognition and treatment of blood pressure overswinging along the 24-hour scale—a must in anti-aging medicine—may prevent postcatastrophic care for years.

A Perspective on the Proposed Association of Melatonin and Aging

Summary: Melatonin is another substance that we need more data on but doesn't look all that promising.

Interestingness: 1

Paper by Russel J Reiter, Dun-Xian Tan, Seok Joong Kim, Javier Cabrera and Daniele D'Arpa in the Journal of Anti-Aging Medicine, Volume 1, Issue 3, Fall 1998.

(((Melatonin is a molecule produced by the pineal gland that regulates the circadian rhythm. It puts you to sleep. It gets produced in the darkness, and bright light interrupts its production)))

Melatonin is another hormone which the body produces less of as it gets older. A graph with a linear best fit seems to indicate that peak melatonin concentration drops by about half between the ages of 20 and 70, although the text mentions a pronounced drop between the ages of 40 and 60. It also mentions factor of two differences between young people of the same age (((which makes it a bit less important in my eyes))). Production of melatonin in calorie-restricted rats drops slower than in normal rats (((probably more of an endorsement of calorie restriction as a method to slow aging than support for melatonin being important in the process)))

(((The paper now switches to melatonin as an anti-oxidant, which doesn't interest me much))) Melatonin mops up hydroxy radicals, peroxyl radicals, and neutralises single oxygen atoms and peroxynitrite anions (ONOO-). It also stimulates activity glutathione peroxidase and glutathione reductase (((dunno how))) which neutralise hydrogen peroxide. The paper stresses the effectiveness in protecting against lipid peroxidation.

Switching to direct aging studies, it mentions a study where the pineal glands of young rats were transplanted into old rats and these older rats were judged to have become younger, a result which the authors of this paper say is hard to accept since the pineal gland stops producing melatonin after the nerves are destroyed (((edit: the author of that paper seemed unhappy with these comments on this paper, and wrote to the editor in the next issue. They do not think the effect is mediated by restoring melatonin levels. Maybe I'll read their paper))) (((edit 2: paper seems reasonable. Part of it is the drugging of the water with interesting results. The pineal transplantations are into the other mice's (not rats) thymus, because they are supposedly similar tissue. Tiny samples, 15 mice transplanted with pineal glands total, but quite a strong effect (810 days vs 747 days mean survival on mice operated on in the 20th month). Probably completely unrelated to melatonin though.))) (((For reference, other paper is "Pineal Control of Aging: Effect of melatonin and pineal grafting on aging mice" by Walter Pierpaoli and William Regelson)))

Studies of long term melatonin administration in rats have had inconclusive results. Drugging the drinking water extended lifespan when it was given during the night but not during the day. Injecting melatonin directly extended lifespan when done in the morning, but not in the afternoon. (((These studies were done on groups of 10 and 15 mice respectively. The second one focuses on the effect of injections of lithium chloride, and melatonin has no effect on top of lithium chloride. The effects look sort of interesting to me, but this paper doesn't think much of them)))



Abstract follows:

Melatonin, the chief secretory product of the pineal gland, has been proposed to have some functional association with aging. Certainly, melatonin production in vertebrates, including humans, wanes with increasing age. This age-related drop in melatonin has been inferred to be consequential in terms of accelerating some aspects of aging, although the experimental evidence for this is not compelling at this point. There are several functional aspects of melatonin that make it of interest to gerontologists. Thus, the cyclic production of melatonin is reflective of the biological clock, and circadian disturbances in general are a feature of aging. These alterations may impact the rate of aging. Also, melatonin is an antioxidant and, as such, it reduces free radical damage. A primary theory of aging is accumulated oxidative damage, and any molecule, such as melatonin, that retards the accumulation of that molecular damage may forestall some aging processes. The experimental data are incomplete, however, and the specific association of the diminished melatonin cycle with aging or age-related diseases remains suggestive but unproven.

Effectiveness of Growth Hormone (GH) Secretagogues in Diagnosing and Treating GH Secretory Deficiency in Aging Men

Summary: Growth hormone releasing peptide (GHRP) increases effect of growth hormone releasing hormone on inducing growth hormone release, even when not given immediately prior. GHRP probably blocks somatostatin. Levels of GHRP's natural equivalent probably drop during aging.

Interestingness: 1

Paper by Richard F Walker and Barry B Bercu in the Journal of Anti-Aging Medicine, Volume 1, Issue 3, Fall 1998.

(((Yet another growth hormone paper. This one at least is neatly done, sticking to only one specific issue and comes with an easy conclusion)))

(((In this study, the older group is a bunch of people between 37 and 68, the younger group is between 16 and 21. The results seem to only refer to the male subsets. These groups are tiny, with six people in some, and three in others)))

Old people release way less growth hormone (GH) than young people when given GH releasing hormone (GHRH), but they release about the same GH when given GH releasing peptide (GHRP) (((an artificial peptide found to release GH, not found yet in the body naturally))) in older as in younger people. The amount released due to GHRP is much higher than that produced when GHRH alone is given. The relative effect of GHRP is much higher in older people: young people released 1.5 times as much GH when given GHRP compared to GHRH, but older people released 20.5 times as much when given GHRP compared to GHRH. When given less GHRP, less GH is released (((this is part of what they want to show, making the connection that older people probably have lower levels of GHRP or equivalent))).

GHRP only enhances the effect of the present GHRH though. If GHRH receptors are blocked with antagonists, GHRP doses don't lead to increased GH release. Giving GHRH and GHRP combined also leads to greater release than the sum of the releases when given separately. This is consistent with GHRP acting as a functional blocker of somatostatin.

Giving older people GHRP for 10 days, and then giving them GHRH the day after, released much more GH than without the 10 days of preparation. Since GHRP is metabolysed in minutes, this means that GHRP is not just acting directly ((("GHRH signal transduction" is what the paper calls it))) (((the increases in these priming examples are much lower than the immediately-prior dosing though)))


Abstract follows:

This study was conducted primarily to determine the utility of recombinant growth hormone releasing hormone (GHRH) and xenobiotic GH-releasing peptide (GHRP) administered sequentially or in combination, as diagnostic agents for pituitary-based, GH secretory dysfunction in aging men. The secondary purpose was to test the hypothesis that loss of sensitivity to stimulation with GHRH during aging results, at least in part, from reduced exposure of the pituitary gland to the yet unknown, endogenous compound whose activity is stimulated by GHRP. Increases in serum GH following GHRH administration were significantly lower in older men than they were in adolescent and young adult men. In contrast, changes in serum GH following GHRP were comparable in the younger and older men. Because robust GH secretion in response to administration of exogenous GHRH or GHRP is interpreted as representing adequate concentrations of complementary endogenous GHRP and GHRH, respectively, the data suggested that older subjects were deficient in endogenous GHRP. Accordingly, it was of interest to determine whether priming with GHRP would restore the response to GHRH in these men. Ten consecutive days of priming with GHRP caused the responses to GHRH challenge to be significantly improved compared with responses observed before priming. GH secretion following co-administration of GHRH and GHRP were comparable in both age groups. The results of this study suggest that functional elements of pituitary somatotrophs directly related to expression of GHRH activity are intact during aging, but lose their effectiveness in part because of complementary secretagogue (endogenous GHRP analogy) deficiencies. Whereas priming with GHRP demonstrates the plasticity of GHRH signal transduction mechanisms in aging men, the data do not allow determination of whether GHRH or GHRP receptors or second messengers for either or both of these secretagogues become down-regulated. Future studies are designed to make these determinations and to further investigate and confirm the validaity of using GH scretagogues to reactivate the GH axis in the elderly.

The Involvement of Protein Kinase C-βII in Glucose-Induced Rat Vascular Smooth Muscle Cell Proliferation

Summary: Protein kinase C beta 2 has something to do with cells entering S-phase, at least for vascular smooth muscle cells from rats' aortas.

Interestingness: 1


Paper by Mayumi Yamamoto, Niketa A Patel and Denise R Cooper in the Journal of Anti-Aging Medicine, Volume 1, Issue 3, Fall 1998.

(((All that growth hormone has destroyed my wishes to summarise everything. I'm going to stick to the ones I find interesting, and only write brief highlights of the rest, like in the case of this one)))

(((The abstract says about everything I would write about this paper and is way clearer because I don't understand the result presented)))

Protein kinase C - beta II (PKC-B2) overexpression slowed down replication of vascular smooth muscle cells (VSMC) extracted from rats' aortas (((VSMC proliferation is likely a bad thing for atherosclerosis))). High glucose levels downregulate PKC-B2 in the short term (((but raise it long term))) and speed up VSMC replication. CG53353 is a PKC-B2 inhibitor (((but adding it doesn't seem to speed up replication of VSMC))). It makes the cells ignore the glucose levels with regards to replication speed. Glucose usually speeds up the rate at which cells enter S-phase (((DNA-replication step of cell replication))). This is consistent with PKC-B2 being a controller of when cells go into S-phase (((but the picture seems confusing to me. Why doesn't adding CG53353 raise VSMC replication? It does on cells that overexpress PKC-B2, but not in standard ones. Why?)))


Abstract follows:

The protein kinase C (PKC)-βII modulates glucose-induced cell proliferation in A10 cells, a clonal cell line of vascular smooth muscle cells (VSMC) from rat aorta, which were studied by overexpressing PKC-βII and using a PKC-βII specific inhibitor (CG53353). PKC-βII overexpression was verified by the fourfold increase of PKC enzyme activity and PKC-βII immunoreactivity. Overexpression of PKC-βII attenuated A10 cell proliferation and DNA synthesis through the suppression of cell cycle progression inhibiting the entry of cells into the S phase. High glucose (25 mM) increased and accelerated cell proliferation, DNA synthesis, and the percentage of cells entering the S phase in A10. High glucose down-regulated PKC-βII in A10 cells during the first cell cycle after cell synchronization. CG53353 inhibited glucose-induced cell proliferation and DNA synthesis specifically. These results suggest that PKC-βII has inhibitory functions as a cell cycle checkpoint mediator during the late G1 phase and may regulate the S phase entry. High glucose down-regulates endogenous PKC-βII, which alters its normal role in cell cycle progression, and results in stimulation of VSMC proliferation through acceleration of the cell cycle. CG53353 might release cells from the PKC-βII regulated checkpoint of the cell cycle.