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NSERF Award for Nutrition and Metabolism

Discourse on diabetes, diet, and cell death: steps toward a purpose

Sanjoy Ghosh, M.Sc.*Division of Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver,

Nutrition 21 (2005) 1176–1178www.elsevier.com/locate/nut

British Columbia, Canada

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When I was 12 y old, I traveled with my parents toombay on summer vacation. It was a 20-h journey by

rain. Within a couple of hours, as my initial enthusiasmaned, my eyes fell on a thin old man sitting by theindow. He looked poor, with worn-out clothes and annkempt beard. For some unknown reason, he kept smilingt me, probably sensing my frustration with the relativenactivity of my parents who were busy reading. Soonhereafter, I mustered enough courage to talk to the old manho seemed more interesting to me than a storybook. I doot remember much of our interaction, except for a partic-lar dialogue. He asked me the name of my father. Facedith a relatively easy question, I promptly replied, “Dilipumar Ghosh.” He said, “Good, now what is your grand-a’s name?” I exuberantly answered, “Laxminarayanhosh.” “Good, what is your great-grandpa’s name?” I wasabbergasted and could not respond. He said, “See, you doot know the name of one of your own relatives whoseame has so quickly been forgotten. Try and accomplishomething for which people remember you. Have a purposen life.” Although I was in India for the next 15 y and madeumerous journeys across the subcontinent on train, I neveret that man again. However, those simple words have

emained with me ever since.An obvious additional contributor to my current interests

s my mother, who lost two siblings due to complicationsrising from diabetes, before I was born. Thus, as long as Ian remember, I was expressly warned to stay away fromweets because I would get diabetes like my mom andould have no option but to take those dreadful insulin

njections that my mom took. I abided meekly because I wasure that the ordeal would kill me. My fear of diabetes laterbated when I learned that not all patients with diabeteseed insulin injections, but my curiosity of the diseaseemained.

Being the first “surviving child” in my family, I was

* Corresponding author. Tel.: �604-822-4420; fax: �604-822-3035.

mE-mail address: sanjkghosh@hotmail.com (S. Ghosh).

899-9007/05/$ – see front matter © 2005 Elsevier Inc. All rights reserved.oi:10.1016/j.nut.2005.07.005

verprotected and was not allowed to take any risks, includ-ng playing outside alone. Having parents who were in-olved with their careers meant that on most afternoons Iemained at home. Because television was unavailable, andideo games did not exist, I spent all that time readingnything to pass the time. These included comic books,agazines, newspaper, and, toward the end, even my moth-

r’s medical books. All that reading accomplished an en-husiasm for reading and a curiosity for medicine. Later onn high school, because the laws of physics and the theoremsf calculus betrayed me, I failed to gain admission intoedical school. Soon thereafter, however, I joined the phar-acy school as the “next best thing.” I am so glad that I did.n graduation from the Bachelor of Pharmacy program

rom Bangalore University, India, I was ranked ninth over-ll among 800 students who took this provincial programnd was given the opportunity to work as a lecturer ofharmacology in the same school. My mentors at the phar-acy school insisted that I pursue a research career. Be-

ause I was familiar with diabetes, I applied to variousniversities with the intent to pursue diabetes research asart of my graduate studies.

In 2000, I was admitted into the Masters Program at Theniversity of British Columbia, under the supervision of Dr.rian Rodrigues, and came to Canada. Unlike most of thether students who come to Canada with an advanced de-ree, I was a newcomer to this exciting but challengingeld. The first class I took was in biochemistry and dealtith “G-proteins.” The only G that I was familiar with was

he gravitational unit in physics! As I staggered through thisourse of “bioche-mystery” for the next few weeks, I camecross the concept of “regulated cell death” (apoptosis)uring one of the lectures. Until that time, I knew that lifeas full of rules and regulations, and the fact that death can

lso be regulated was intriguing. My interest in this topicrew in leaps and bounds. Interestingly, because the sciencef “cell death” encompassed all the major elements ofiochemistry from protein folding to energetics, I soon

astered the entire course. As a part of the final examina-

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1177S. Ghosh / Nutrition 21 (2005) 1176–1178

ion, we had to write a “grant proposal” on any one bio-hemistry topic. I wrote a proposal on the role of fatty acidsn cell apoptosis and got an A. My success in my coursesade my supervisor, Dr. Rodrigues, very happy, but at the

ame time he pressed me to start my own research project.ne of the best things about Dr. Rodrigues is that he is open

o any kind of idea on research as long as the topic dealtith the heart and concerned diabetes. The timing waserfect for me. Around this time, a study was published thatemonstrated that human diabetes is characterized by in-reased apoptosis in the heart, which could play a role in theevelopment of diabetic heart disease, the greatest killer ofatients with diabetes [1]. Because the science of diabetesas fairly “glucocentric,” the role of dyslipidemia in dia-etic heart disease was still controversial. Our question wasretty simple: Can the increase in fatty acids seen duringiabetes contribute to myocardial cell death and cardiacysfunction? Although we were interested in the question,e did not have any funds to examine this particular ques-

ion.r. Rodrigues encouraged me to come up with a grantroposal on the question, so that we could apply for fund-ng. Under his supervision, I worked fervently and trans-ormed my two-page grant proposal in the biochemistryourse to a 10-page proposal that was submitted to the Heartnd Stroke Foundation of Canada. Excitingly, our effortsere rewarded and our grant was funded.Because I worked primarily in a cardiac metabolism

aboratory, I gained considerable knowledge in the meta-olic aspects of cardiac disease. This proved to be an assets we started to look at cell death, not simply from theolecular angle but also from a physiologic, whole-animal

iewpoint. I was also lucky to have extremely intelligentnd helpful colleagues in my laboratory who provided meheoretical and practical help with my studies. As we startedur research in this relatively new field of cell death in theiabetic heart, we noticed that majority of the existingeports dealt with in vitro studies. Under in vitro conditions,ardiac cells were incubated with mainly saturated fattycids such as palmitic acid to induce death. The flaws withhis approach were that the heart is provided with more thansingle fatty acid at a given time and that the supply of free

atty acids is made possible through hydrolysis of circulat-ng lipoproteins, which account for most fatty acids sup-lied to the heart. Another striking feature of these in vitrotudies was the high incidences of apoptosis (often as manys 40% of the total cell population died), whereas in vivonly 1% to 2% of cells undergo apoptosis at a given time.e hypothesized that this exaggerated death response in

itro was probably reflective of decreased energy demand ofon-beating, quiescent cells, which were not able to prop-rly oxidize fatty acids leading to increased fatty acid de-ivery to cell death pathways. Thus, it was imperative thate consider in vivo models of dietary fatty acids to properly

valuate the effects of increased fatty acid supply to the

eart. d

To investigate the cardiac effects of saturated fat duringyperglycemia, we fed a group of rats a diet based on palmil followed by induction of diabetes. Interestingly, andurprisingly, we noticed that in the group fed a diet based onunflower oil (used as an isocaloric control), there was aigh mortality within 3 d of diabetes induction. On closexamination of the heart, we noticed a sluggish heartbeatnd a flaccid appearance. On more detailed examination, weetermined that, unlike hearts in the palm oil group, those inhe sunflower oil group had developed severe cardiac ne-rosis, another form of cell death that is far more damagingo the myocardium.

Sunflower oil is primarily composed of linoleic and ar-chidonic acids, which belong to a class of �-6 polyunsat-rated fatty acids (PUFAs). It has long been documentedhat PUFAs are generally beneficial for health and antiath-rosclerotic in nature. When we did a literature search onhe effects of PUFA in diabetes, we were surprised to seehat not much work had been reported in this area. Most ofhe beneficial effects of PUFA have been traditionally dem-nstrated in men who did not have diabetes but did haveoronary artery disease. The dilemma is that, as majority ofhe diabetic population develops coronary artery disease,UFAs as a “good thing” for patients without diabetes islso recommended unwittingly to those who have diabetes.e hypothesized that, because diabetes per se can increase

eneration of free radicals that are known to be a causativelement behind all major diabetic complications [2], havingigh levels of highly oxidizable PUFA in cardiac mem-ranes could lead to increased damage. In humans, serumnd adipose tissue linoleic acid levels have been stronglyorrelated to an increased risk of myocardial infarction andecrosis. In support of our hypothesis, we found out thatarious other laboratories also reported the damaging ef-ects of �-6 PUFA in vitro, which, although not apoptotic inature, caused cell death nonetheless.

The other intriguing factor was that most coronary vas-ular benefits have been attributed to �-3 PUFAs such asicosapentaenoic acid and docosahexaenoic acid and not to-6 PUFAs. However, because the North American diet is

carce in fish oils, the richest source of �-3 PUFAs, depen-ence on the other kind of PUFA (i.e., �-6 PUFA) hasncreased. In addition to the intentional modification ofuman dietary intake described above, farmed animals areed grains and seeds containing high amounts of �-6 PUFA.onsumption of these animals (and their products) has led

o an even greater increase in dietary �-6 PUFA [3]. Thus,lthough the total amount of dietary fat has not changedignificantly, �-6 PUFA has increased up to 10% of totalnergy intake [4]. When expressed as a ratio, from a bal-nced 1:1, the present �-6:�-3 PUFA ratio has increased ton astounding 15:1 to 20:1 in the Western diet.

After all these observations, we were still intrigued byhe question as to why the necrotic effects of �-6 PUFAere not reported earlier. We found out that most studies

one with fat feeding in diabetes had been performed with

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1178 S. Ghosh / Nutrition 21 (2005) 1176–1178

ard, composed mainly of saturated fatty acids known toxert the apoptotic death pathway, or by a high-fat diet withbalanced �-6:�-3 ratio. In addition, current techniques of

stimation of in vivo apoptosis such as the terminal de-xyuridine triphosphate nick end labeling assay is not veryfficient in excluding necrotic cell death [5]. Although ap-ptotic cell death may induce characteristic DNA fragmentshat can be picked up by specific antigens and repair en-ymes, necrosis (characterized by cell bursting) is extremelyard to quantify.

Since our discovery of the pronecrotic phenomenon in �-6UFA-fed diabetic hearts, published first in Nutrition [6], weave subsequently documented mechanisms for such celleath in the American Journal of Physiology [7]. Work hasust begun in our laboratory in this exciting and new area,nd many questions remain unanswered. At this crucialuncture, we were very excited to hear the news of ourriginal paper receiving the NSERF Award for Nutritionnd Metabolism and this award confirms that we are in theight direction. This recognition reaffirms our faith and thatf the scientific community in our goal to make a difference.f we could reinforce the fact that “all that is PUFA is notealthy” and that the current epidemic in diabetic cardio-

ascular disease is partly due to over dependence on �-6

UFAs in our diet, it will give our “bench” research clinicalpplicability and me, a “purpose.” Not to mention, the oldan from the train would be exceedingly happy!

eferences

1] Frustaci A, Kajstura J, Chimenti C, Jakoniuk I, Leri A, Maseri A, et al.Myocardial cell death in human diabetes. Circ Res 2000;87:1123–32.

2] Brownlee M. Biochemistry and molecular cell biology of diabeticcomplications. Nature 2001;414:813–20.

3] Simopoulos AP. Essential fatty acids in health and chronic disease.Am J Clin Nutr 1999;70:560S–9.

4] Jenkinson A, Franklin MF, Wahle K, Duthie GG. Dietary intakes ofpolyunsaturated fatty acids and indices of oxidative stress in humanvolunteers. Eur J Clin Nutr 1999;53:523–8.

5] Ohno M, Takemura G, Ohno A, Misao J, Hayakawa Y, MinatoguchiS, et al. “Apoptotic” myocytes in infarct area in rabbit hearts may beoncotic myocytes with DNA fragmentation: analysis by immunogoldelectron microscopy combined with In situ nick end-labeling. Circu-lation 1998;98:1422–30.

6] Ghosh S, An D, Pulinilkunnil T, Qi D, Lau HC, Abrahani A, et al. Roleof dietary fatty acids and acute hyperglycemia in modulating cardiaccell death. Nutrition 2004;20:916–23.

7] Ghosh S, Qi D, An D, Pulinilkunnil T, Abrahani A, Kuo KH, et al.Brief episode of STZ-induced hyperglycemia produces cardiac abnor-malities in rats fed a diet rich in n-6 PUFA. Am J Physiol Heart Circ

Physiol 2004;287:H2518–27.