The Biology of Obesity

Obesity in the United States has reached staggering proportions where 34% of the population is considered to be obese. The measure of obesity is the so-called “body mass index (BMI) that represents the ratio between a person’s weight in pounds multiplied by 703 (a constant) over the height in inches taken to the second power – Weight (in pounds) X 703/ (height in inches) 2. For example an individual weighing 190 pounds and with a height of 66 inches would have a BMI of (190 * 703)/ (66 inches) 2 which is equal to 30.6. A BMI greater than 30 is defined as obese and a value of over 25 is considered overweight.

The BMI was originally developed by the Belgium statistician Adolphe Quetelet (1796-1874). It is important to note that this value does not measure body fat directly, but it is a useful indicator of obesity that is recognized throughout the world.

There are many factors that contribute to obesity in the American culture. This is, however, beyond the scope of this overview. We will examine, instead, what is currently understood regarding the biology of obesity. Current understanding seems to point to three different systems of the human body that contribute to obesity – namely, the nervous system –the brain, metabolism and the genetics. We will examine these in turn.

It has long been known that the areas of the brain including the hypothalamus and the brain stem are involved in regulating the feelings of hunger and fullness. In addition, current data provided by functional magnetic resonance imaging (FMRI) that allows an investigator to visualize metabolically active parts of the human brain have also implicated the so-called pleasure reward centers of the limbic system and the prefrontal cortex. It seems that overeating, in effect, mimics drug addiction. This understanding may eventually prove useful in the treatment of obesity.

It seems that some adult men and women have retained stores of brown fat from childhood. Unlike white fat, brown fat is associated with leanness and its main function seems to be the generation of heat; whereas, white fat is involved primarily in storing energy. In some ways brown fat seems to be closely related to muscle. It remains to be seen what the factors are that predispose certain individuals to retain brown fat.

Variations in twenty separate genes have been implicated in regards to obesity; however, their cumulative contribution would be too small to account for the marked prevalence of obesity in the general population. This does not preclude the contribution of environmental factors in activating or suppressing certain genes and contributing to obesity in this way. Such genetic switches have been discovered in mice, suggesting that analogous mechanisms operate in humans.

Understanding the biology of obesity is an essential step in determining the best ways to treat this growing epidemic that has become strongly associated with modern life and culture.

The Negative Impact of Loneliness on Human Health

Loneliness is a common experience in human life.  It may arise from the ordinary vicissitudes of living.  Loneliness, on occasion, confronts all individuals in all walks of life and at all stages of life.  It is a quite normal and natural phenomenon. 

However, a condition of chronic loneliness has been shown to have more serious implications.  John Cacioppo, a social psychologist from the University of Chicago, has been engaged in protracted studies regarding the biological effects of a chronic state of aloneness.  As a result of his numerous investigations, he, with the help of his collaborators, has discovered changes that occur in the cardiovascular, immune and nervous systems in chronically lonely individuals.  In fact, it has been well established that individuals suffering loneliness have increased mortality.

Cacioppo has been involved in the study of the human brain's role in social behavior and is, in fact, credited with being a founder of the discipline of social neuroscience.   As a result of his extensive studies into loneliness, he has come up with some very important findings.

It is the perception of loneliness that seems to be more important than the number of social contacts a person may have.  This perception has definitive physiological impacts that adversely affect health.  It seems that lonely people have an activated sympathetic nervous system; this system is involved with the flight or fight response.  The neuro-transmitters that are produced as a result of this response, epinephrine and cortisol, lead to the constricting of blood vessels that increase blood pressure and put added stress on the heart.  In addition, the subjective feeling of loneliness impacts the immune system, resulting in an increase in the inflammatory response – implicated in heart disease – and a decrease in the capability of the body to fight viral infections.   It has also been reported that the area of the brain, the ventral striatum, implicated in the brain's reward circuitry has been shown to have decreased activity in lonely people as compared to "normal" controls.  Some genetic susceptibility to this state of mind has also been shown.

These data strongly suggest that loneliness has an adverse impact on the quality of life and the general health of those who suffer from it.  It is somewhat troubling that modern life seems to make individuals even lonelier.  The current estimate – as compiled by the U.S.  Census Bureau - is that 29% of the population lives alone; this represents a 30% increase from 1980.

Global Impact of the Rising Sea

There are many complex and interrelated facets to the consequences that result from the increasing level of Carbon Dioxide (CO2) in the earth’s atmosphere. A common misconception is that the apparent increases in the severity of winter in many parts of the United States refute the urgent need to introduce public policy that would seriously control CO2 emissions. Quite to the contrary, dramatic changes in climate that are evidenced throughout the world reinforce the serious nature of the impact of the accelerated release of green house gases into the atmosphere on global climate.

One of the more disturbing consequences of climate change is the potential for a significant rise in the sea level. Of particular interest are the consequences an increase in the sea level would have on the inhabitants of the Mekong Delta in Vietnam. This area is inhabited by 18 million people - a number that represents 22 percent of the entire Vietnamese population and accounts for 40 percent of the country’s cultivated land. In this fertile region, food production accounts for more than half the rice, 60% of the fish and shrimp and 80% of the fruit crop for the entire nation.

This area is especially vulnerable to sea level rise. Periodic flooding has played a significant role in the life of the peoples of the Mekong Delta. As a matter of fact, flood depths from a half a meter to three meters represent what is considered to be within the normal range. Such a level of flooding is referred to “nice floods” by those living in the area. However, more severe flooding can have a dramatic impact on the ability of the residents to cope.

In fact, both the frequency and magnitude of the flooding that exceeds four meters have increased. As a consequence, Individuals and families from this region are making the decision to seek another livelihood, preferably in the cities.

Using computer modeling, it has been estimated that one meter rise in sea level would impact seven million people living on the delta and a two meter rise would adversely affect fourteen million people – 50 percent of the delta population. Although current models for sea level rise do not anticipate such dramatic increases, unforeseen possibilities such as the accelerated melting of land-locked on Greenland and West Antarctic could dramatically change these predictions.

Given this information, it would be advisable for governments throughout the world to formulate policies with the purpose of curtailing the outpouring of CO2 into the atmosphere.

Asymptomatic HIV Positive Individuals – How are they different?

AIDS is a horrific disease characterized by a severely compromised immune system. Without a competent immune system, the body is unable to combat infectious diseases and non-infectious ailments such as cancer. It has, of course, been well established that AIDS is a result of an infection caused by HIV-1, a retrovirus that preferentially attacks Helper T cells (CD4+) – cells that are primary players in a functioning immune system. The symptoms characteristic of AIDS ordinarily show themselves once the number of circulating CD4+ cells reaches a dangerously low level. There is a direct correlation between the number of viral particles circulating in the blood – the so-called “viral load” – and the onset of symptoms. Most infected individuals demonstrate a viral load exceeding 10,000 viral copies/ml of blood. The new life-saving therapeutic drugs are able to decrease this viral load substantially.

There are a small number of HIV-1+ individuals, however, who have depressed viral loads without the use of drugs. These individuals are collectively referred to as HIV Controllers. They show stable and normal levels of CD4+ cells, do not show signs of disease and are less likely to be infectious.

It would, therefore, invaluable to understand what makes HIV Controllers different. There is for this reason a large study underway to unravel this mystery. This study is referred to as The International HIV Controllers Study with literally hundreds of contributing scientists from around the world. One of the goals of this study is to discover the genetic basis for this apparent advantage shared by HIV Controllers. To do this, genomic DNA – the full complement of DNA within an individual – was sampled from Controllers and Progressors – those HIV-1 -infected individuals who progress to full blown disease - and subsequently compared between these two groups. The results reported in the December 10, 2010 edition of the renowned scientific journal Science showed that there were over 300 single nucleotide polymorphisms (SNPs) within the major histocompatibility complex (MHC). The MHC region in the human genome has been shown to have strong genetic associations with infection and inflammatory diseases.

To quote the authors, “Altogether, these results link the major genetic impact of host control of HIV-1 to specific amino acids – the chemical building blocks of protein - involved in the presentation of viral peptides – small protein molecules - on infected cells. This represents a significant finding that helps elucidate the nature of the protection that Controllers naturally possess and may eventually prove useful in devising therapies against AIDS.

Asthma and Bacteria – A Possible Link

Asthma remains a baffling disease that impacts a growing number of individuals, especially children. Asthma is characterized by a constriction and swelling of the airways. The symptoms include the production of mucus and more importantly coughing, wheezing and a shortness of breath. Currently there is no cure for this condition but medications can be used to control it. The severity of this disease varies widely; it can be vary from a nuisance to a life threatening condition.

Recent evidence suggests that there is a strong connection between asthma and the kinds of bacteria that the body ordinarily harbors. Some years ago, Dr. Gary Huffnagle, an immunologist from the University of Michigan, subjected experimental mice to yeast introduced into their intestines; mold spores placed in their noses and an antibiotic drug. These animals began showing signs of asthma and blood tests indicated immune system dysfunction.

In addition, studies have indicated that children raised on farms are much less prone to suffer from diseases of the lung, including asthma, and Dr. William Cookson, a respiratory physician from the Imperial College of London, suggests that exposure to a diverse bacterial environment in childhood may play a protective role. Additionally, children born via the sterile environment of a cesarean section are more prone to suffering from asthma than those that have passed through the birth canal, and children that have had multiple courses of antibiotics are more likely to have asthma than their counterparts.

The relationship between asthma and the bacteria that ordinarily reside within the body is an exceedingly complex one. Yet, it has become clear that children who are stricken by asthma have different bacteria within their bodies and often a less diverse population than non-asthmatic children. The findings of these studies reinforce what has long been suspected regarding asthma,

Deepwater Horizon Blowout - Existence of Undersea Plumes of Oil

The environmental catastrophe caused by the blowout of the Deepwater Horizon at the Macondo well site resulted in the largest offshore oil spill in history. Although much of the surface oil contamination has been significantly mitigated, there remains an issue regarding the existence of undersea hydrocarbon plumes.

These plumes have been tracked by Dr. Richard Camilli and his colleagues from the department of Applied Ocean Physics and Engineering at the Woods Hole Oceanographic Institution. As a result of the blowout, more than 4 million barrels of oil were released into the Gulf of Mexico. Since the source of the spill was some 1500 meters beneath the surface, this resulted in the formation of undersea plumes of oil. On account of the complex variables that are involved in plume formation – the interplay of gas and oil in multiphase flow and the solubility of each of the constituents in the complex mixture - , it is exceedingly difficult to derive models that can reliably predict the behavior of hydrocarbons under such conditions.

In spite of the daunting problems associated with this catastrophe, the investigators were able to detect and measure the hydrocarbon plumes. They discovered the presence of a continuous plume of oil more than 35 kilometers in length at an approximate depth of 1100 meters. This plume persisted for months without signs of significant biodegradation.

Further studies by other investigators, however, have shown that the presence of the plume stimulated the growth of bacteria that are known to degrade hydrocarbons. The encouraging aspect of their findings is that, “the potential exists for intrinsic bioremediation of the oil plume in the deep-water column without substantial oxygen drawdown.”

The existence of undersea hydrocarbon plumes in the Gulf of Mexico has inspired scientific investigators to study their properties. The results of their work may lead to strategies designed to counter the ill effects of similar human catastrophes should they happen in the future.

Virus Discovered as a Causative Agent in a Disease Prevalent in Central China

There have been many reported cases of a deadly fever outbreak in Central China. Numerous instances have been reported for the last three summers. The inexplicable illness is characterized by high fever and gastrointestinal distress (GI). Many of the individuals impacted by this illness bled severely, and, most alarmingly, as many as 30% of the victims have died. At first, scientists at the Chinese Center for Disease Control and Prevention (CDC) postulated that the disease was a form of human granulocytic anaplasmosis (HGA) a bacterial infection spread through tick bites.

Xue-jue Yu, a visiting scientist studying this illness at the Chinese CDC’s National Institute of Communicable Disease Control and Prevention (NICDC), was skeptical of this explanation. According to him, the mortality was too high, and, more conclusively, examination of blood samples did not reveal the presence of Anaplasma phagocytophilum - the bacterial agent that is responsible for HGA. Pursuing this problem, his team finally discovered a new type of bunyavirus as the culprit. Members of this family of viruses include the hantavirus and the Rift Valley fever virus. Hantavirus is responsible for a serious illness referred to as hantavirus pulmonary syndrome (HPC) spread by infected rats to humans. Yu’s results were subsequently reported in the New England Journal of Medicine (NEJM).

This is a rather disturbing finding and may point to the emergence of a new virus with a potentially deadly outcome for those infected. It is certainly worth increased attention on the part of public health professionals throughout the world.