Exercise, Abdominal Fat, Insulin Resistance

Researchers writing in The Journal of Applied Physiology studied 16 obese men and women, about 63 years old, during a 12 week exercise program. During the program the participants exercised 5 days a week for 60 minutes a day (treadmill/cycle ergometry @ 85% of heart rate max). Among the many things the researchers measured was total abdominal fat, subcutaneous fat (fat under the skin) and visceral fat (the fat that surrounds the organs).

From the study abstract: “Exercise improves glucose metabolism and delays the onset and/or reverses insulin resistance in the elderly by an unknown mechanism. In the present study we examined the effects of exercise training on glucose metabolism, abdominal adiposity and adipocytokines* in obese elderly.”

What the researchers found: “Visceral fat loss after aerobic exercise training improves glucose metabolism and is associated with the reversal of insulin resistance in older obese men and women.”

*Adipocytokines are a collective term for secretions from the fat cells that help regulate energy metabolism and food intake among other functions.

Reference: O’Leary VB, Marchetti CM, Krishnan RK, Stetzer BP, Gonzalez F, Kirwan JP. Exercise-induced reversal of Insulin Resistance in Obese Elderly is associated with reduced Visceral Fat.J Appl Physiol (December 22, 2005) Study abstract

Insulin Resistance and Metabolic Syndrome

Insulin Resistance Tied To Age-Related Muscle Loss
Writing in the medical journal Diabetes and Metabolism, researchers say: “…insulin resistance could be involved in age-related muscle protein loss, progressively leading to sarcopenia. Therefore in a more general concept, insulin resistance found in many clinical settings, could be considered as a contributor to muscle wasting.”

Insulin Resistence: What Do Some Researchers Say?
When we eat, our bodies release insulin into our blood stream so that we can process glucose (sugars) from our foods to make energy, especially in our muscles. Glucose belongs in our cells and not in our blood. When it remains in our blood we produce more insulin. Increased insulin, according to many researchers, is the number one factor for accelerated aging.

What is the Effect of Insulin Resistance and Loss of Lean Muscle (Sarcopenia) As We Age?
Researchers writing in the Journal of The Federation of American Societies for Experimental Biology say: “A reduced response of older skeletal muscle to anabolic stimuli (exercise & diet) may contribute to the development of sarcopenia. Skeletal muscle protein synthesis is resistant to the anabolic action of insulin in older subjects, which may be an important contributor to the development of sarcopenia.”

Metabolic Syndrome and Stroke
Researchers writing in the Archives of Internal Medicine say that preventing and controlling Metabolic Syndrome is likely to reduce risk of stroke.

Stress at Work and Metabolic Syndrome
Metabolic Syndrome is a combination of symptoms including high blood pressure, abdominal obesity, insulin resistance and others related to coronary heart disease.

Pregnenolone Research

Sleep and Memory

George O, Vallee M, Le Moal M, Mayo W. Neurosteroids and cholinergic systems: implications for sleep and cognitive processes and potential role of age-related changes Neurosteroids and cholinergic systems: implications for sleep and cognitive processes and potential role of age-related changes. Psychopharmacology (Berl). 2006 Jan 17;:1-12

Rationale: The neurosteroids pregnenolone sulfate (PREGS), dehydroepiandrosterone sulfate (DHEAS) and allopregnanolone (3alpha,5alpha THPROG) have been implicated as powerful modulators of memory processes and sleep states in young and aged subjects with memory impairment. As these processes depend on the integrity of cholinergic systems, a specific effect of neurosteroids on these systems may account for their effects on sleep and memory.

Objective: To review the evidence for a specific and differential effect of neurosteroids on cholinergic systems.

Conclusions: The specific modulation of basal forebrain and brainstem cholinergic systems by neurosteroids may account for the effects of these compounds on sleep and memory processes. To improve our understanding of the role of neurosteroids in cholinergic systems during normal and pathological aging, we need to determine whether there is specific regionalization of neurosteroids, and we need to investigate the relationship between neurosteroid concentrations in cholinergic nuclei and age-related sleep and memory impairments.

Alzheimer’s
Neurosteroid quantification in human brain regions: comparison between Alzheimer’s and nondemented patients.

Weill-Engerer S, David JP, Sazdovitch V, Liere P, Eychenne B, Pianos A, Schumacher M, Delacourte A, Baulieu EE, Akwa Y.Neurosteroid quantification in human brain regions: comparison between Alzheimer’s and nondemented patients.J Clin Endocrinol Metab. 2002 Nov;87(11):5138-43

Abstract: “…To investigate the physiopathological significance of neurosteroids in Alzheimer’s disease (AD), we compared the concentrations of pregnenolone, pregnenolone sulfate (PREGS), dehydroepiandrosterone, dehydroepiandrosterone sulfate (DHEAS), progesterone, and allopregnanolone…in individual brain regions of AD patients and aged nondemented controls, including hippocampus, amygdala, frontal cortex, striatum, hypothalamus, and cerebellum.

A general trend toward decreased levels of all steroids was observed in all AD patients’ brain regions compared with controls: PREGS and DHEAS were significantly lower in the striatum and cerebellum, and DHEAS was also significantly reduced in the hypothalamus. A significant negative correlation was found between the levels of cortical beta-amyloid peptides and those of PREGS in the striatum and cerebellum and between the levels of phosphorylated tau proteins and DHEAS in the hypothalamus. This study provides reference values for steroid concentrations determined by gas chromatography-mass spectrometry in various regions of the aged human brain. High levels of key proteins implicated in the formation of plaques and neurofibrillary tangles were correlated with decreased brain levels of PREGS and DHEAS, suggesting a possible neuroprotective role of these neurosteroids in AD.”

Pregnenolone main page

Hormones, Oxidative Stress, Menopause

In the News…
Researchers writing in Clinica Chimica Acta, the International Journal of Clinical Chemistry and Applied Molecular Biology suggest that Hormone Replacement therapy may play a beneficial role in the protection against oxidative stress.

Clin Chim Acta. 2006 Jul;369(1):73-7. Epub 2006 Feb 10.
Unfer TC, Conterato GM, da Silva JC, Duarte MM, Emanuelli T. Influence of hormone replacement therapy on blood antioxidant enzymes in menopausal women. Clin Chim Acta. 2006 Jul;369(1):73-7. Epub 2006 Feb 10.

From the abstract:
BACKGROUND: Natural loss of estrogen occurring in menopausal process may contribute to various health problems many of them possibly related to oxidative stress. Hormone replacement therapy (HRT) is the most common treatment to attenuate menopausal disturbances. This study was aimed at evaluating the influence of HRT on the activity of antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT; and glutathione peroxidase, GPx) and lipid peroxidation (thiobarbituric acid reactive substances, TBARS) in menopausal women.

CONCLUSIONS: HRT antagonizes the decrease of SOD activity that occurs after menopause, suggesting that HRT may play a beneficial role in the protection against oxidative stress.

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