For those who smoke young...

August 25, 2003

August 25, 2003 - (Bethesda, MD) - The dangers of cigarette smoking are well known, and each day America's young people are exposed to a number of public and privately sponsored anti-tobacco campaigns. Despite the best efforts of health educators, children and adolescents become regular tobacco users each day.

Many take up the habit believing that if they stop at a relatively young age there will be no long-term adverse consequence to their health. Unfortunately, these same young people are unaware that cigarette use has been linked to insulin resistance and insulin-dependent glucose metabolism. Insulin resistance is known to be a major risk factor in the development of adult-onset diabetes, a disease reaching epidemic proportions. Scientists also suggest there may be a dose-response relationship between smoking and the risk of diabetes.

Impaired insulin-stimulated muscle glycogen synthesis is an early defect in the cause of diabetes and is present in individuals at high risk of diabetes before the development of impaired glucose tolerance

Why? Significant differences in glycogen replenishment can be attributed to hormone insulin. Insulin is released by the pancreas in response to carbohydrate consumption. The hormone's many functions include the transportation of glucose into liver and muscle tissues and to stimulate the synthesis of carbohydrate into muscle glycogen, which is how the muscle stores energy. Because insulin is essential in replenishing muscle glycogen after exercise, researchers have focused on enhancing insulin release during recovery. It is well known that increasing the amount of carbohydrate consumed will increase insulin levels and result in more muscle glycogen storage.

Postexercise muscle metabolism plays a major role in systemic carbohydrate balance and may be influenced by smoking. Although the association of cigarette smoking with insulin resistance and impaired glucose tolerance has been established through previous research, the question of whether this smoking affects the final step in the physiological process -- impaired muscle glycogen storage - has yet to be addressed.

A New Study

Accordingly, a new study was undertaken to determine whether the insulin-dependent phase of postexercise muscle glycogen synthesis is impaired in a fasting population of young healthy cigarette smokers. The authors of "Smoking Impairs Muscle Recovery from Exercise" are Thomas B. Price, Suchitra Krishnan-Sarin, and Douglas L. Rothman, all from the Yale University School of Medicine, New Haven, CT. Their research appears in the July 2003 edition of the of the American Journal of Physiology--Endocrinology and Metabolism. The journal is one of 14 published each month by the American Physiological Society (APS).

Methodology

To evaluate smoking-induced effects on carbohydrate metabolism, the researchers studied muscle glycogen recovery from exercise in a young healthy population of eight smokers and ten non-control subjects. The study used spectroscopy to compare muscle glycogen and glucose 6-phosphate (G-6-P) levels during recovery in exercised gastrocnemius muscles of randomized cohorts of healthy male smokers and a control group. The smokers consumed at least 20 cigarettes/day; their age was 24 ± 2 years, and they weighed 70 ± 4 kg. The control group of ten non-smokers was of similar age and weight. Subjects performed single-leg toe raises to deplete glycogen to approximately 20 mmol/l, and glycogen resynthesis was measured during the first four hours of recovery. Plasma samples were assayed for glucose and insulin at rest and during recovery.

Results

The findings revealed that gastrocnemius glycogen concentrations were similar in smokers and controls. Exercise-induced glycogen depletion data indicate that both groups depleted similar amounts of glycogen over a similar period of time while performing a similar amount of work. After exercise, there was steady glycogen resynthesis for approximately one hour that was similar in both groups. During the four hours of recovery, steady glycogen synthesis continued at a reduced rate in the control group; however, glycogen synthesis ceased in the smokers. During this recovery period, the glycogen synthesis rate in the smoking group was 74 percent lower than in the control group. Total glycogen recovery over the four-hour measurement period was significantly greater (1.9-fold) in controls than in smokers.

Baseline concentrations of G-6-P, Pi, PCr, and the intracellular pH were similar in the two groups. Throughout the four-hour postexercise measurement period, Pi and PCr concentrations and intracellular pH were similar between the two groups. During the first hour of recovery, G-6-P levels were not significantly different between the two groups. However, over the subsequent three hours of recovery, mean G-6-P concentrations were significantly lower in the smoking group (52 percent lower) compared with the control group.

The plasma glucose concentrations were not significantly different between groups and controls, nor were they different after exercise. Baseline insulin levels were also similar between the smokers and controls. Plasma insulin levels were not significantly different between smokers and controls during the first hour of recovery or during the insulin-dependent period (four hours of recovery).

Conclusions

This study reports that insulin-dependent muscle glycogen synthesis is impaired in a healthy population of young smokers, much like that observed in prediabetic subjects. This is, to their knowledge, the first report of smoking-induced alteration of skeletal muscle glycogen synthesis.

An important systemic factor in postexercise muscle glycogen recovery is the efficiency with which plasma glucose is delivered to the exercised muscle. Although cigarette smoking has been shown to inhibit nitric oxide (NO) bioactivity, thereby enhancing vasoconstriction, insulin induces NO-mediated widening of the blood vessels. The findings point to an association between insulin and NO in the vasodilatory response and the impact of cigarette smoking on vasodilation could have exerted an effect on the level of postexercise perfusion of the observed gastrocnemius muscle.

An initial insulin-independent glycogen synthesis rate between the subject and control groups was not significant. However, it is possible that a reduction in flow could have contributed to the slower rate seen in the smokers. It is also possible that early insulin-independent postexercise muscle glycogen synthesis has both an insulin-independent component and an insulin-dependent component. Data from this study can neither confirm nor refute the contribution of impaired blood flow to the observed impairment of postexercise insulin-dependent glycogen synthesis. However, it is clear that the end result is reduced muscle glycogen in smokers after four hours of fasting recovery from glycogen-depleting exercise.
-end-
Source: July 2003 edition of the American Journal of Physiology--Endocrinology and Metabolism.

The American Physiological Society (APS) was founded in 1887 to foster basic and applied science, much of it relating to human health. The Bethesda, MD-based Society has more than 10,000 members and publishes 3,800 articles in its 14 peer-reviewed journals every year.

American Physiological Society

Related Smoking Articles from Brightsurf:

Smoking rates falling in adults, but stroke survivors' smoking rates remain steady
While the rate of Americans who smoke tobacco has fallen steadily over the last two decades, the rate of stroke survivors who smoke has not changed significantly.

What is your risk from smoking? Your network knows!
A new study from researchers at Penn's Annenberg School for Communication found that most people, smokers and non-smokers alike, were nowhere near accurate in their answers to questions about smoking's health effects.

Want to quit smoking? Partner up
Kicking the habit works best in pairs. That's the main message of a study presented today at EuroPrevent 2019, a scientific congress of the European Society of Cardiology (ESC).

Smoking and mortality in Asia
In this analysis of data from 20 studies conducted in China, Japan, South Korea, Singapore, Taiwan and India with more than 1 million participants, deaths associated with smoking continued to increase among men in Asia grouped by the years in which they were born.

Predictors of successfully quitting smoking among smokers registered at the quit smoking clinic at a public hospital in northeastern Malaysia
In the current issue of Family Medicine and Community Health, Nur Izzati Mohammad et al. consider how cigarette smoking is one of the risk factors leading to noncommunicable diseases such as cardiovascular and respiratory system diseases and cancer.

Restaurant and bar smoking bans do reduce smoking, especially among the highly educated
Smoking risk drops significantly in college graduates when they live near areas that have completely banned smoking in bars and restaurants, according to a new study in the American Journal of Epidemiology.

How the UK smoking ban increased wellbeing
Married women with children reported the largest increase in well-being following the smoking bans in the UK in 2006 and 2007 but there was no comparable increase for married men with children.

Smoking study personalizes treatment
A simple blood test is allowing Vanderbilt University Medical Center (VUMC) researchers to determine which patients should be prescribed varenicline (Chantix) to stop smoking and which patients could do just as well, and avoid side effects, by using a nicotine patch.

A biophysical smoking gun
While much about Alzheimer's disease remains a mystery, scientists do know that part of the disease's progression involves a normal protein called tau, aggregating to form ropelike inclusions within brain cells that eventually strangle the neurons.

A case where smoking helped
A mutation in the hemoglobin of a young woman in Germany was found to cause her mild anemia.

Read More: Smoking News and Smoking Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.