Should the Insulin Resistance Syndrome be Treated in the Elderly?

Relationship between sleep parameters, insulin resistance and age-adjusted insulin like growth factor-1 score in non diabetic older patients

BACKGROUND

Sleep complaints are prevalent in older patients. Sleepiness, short or long sleep duration and obstructive sleep apnea (OSA) are associated with insulin resistance (IR). These parameters have not yet been considered together in the same study exploring the possible association between IR and sleep in older patients. IR is involved in cardiovascular and metabolic diseases, pathologies which are highly prevalent in older patients. Here we assess, in older non-diabetic patients with sleep complaints, the associations between IR and sleep parameters objectively recorded by polysomnography (PSG) rather than self-report. The Growth Hormone/Insulin like growth factor-1 axis could play a role in the development of IR during sleep disorders. The second objective of this study was to analyze the association between sleep parameters and age-adjusted IGF-1 score, which could explain the association between OSA and IR.

METHODS

72 non-diabetic older patients, mean age 74.5 ± 7.8 years, were included in this observational study. We evaluated anthropometric measures, subjective and objective sleepiness, polysomnography, Homeostatic Model Assessment for IR (HOMA-IR) and age-adjusted IGF-1 score. A multivariate regression was used to determine factors associated with HOMA-IR.

RESULTS

The 47 OSA patients were over-weight but not obese and had higher IR than the non-OSA patients. In multilinear regression analysis, apnea-hypopnea index was independently associated with IR after adjustment for several confounding factors. Neither IGF-1 level nor IGF-1 score were different in the two groups.

CONCLUSIONS

We demonstrate that in non-diabetic older patients with sleep complaints, OSA is independently associated with IR, regardless of anthropometric measurements and sleep parameters (sleep duration/sleepiness/arousals). Targeting OSA to reduce IR could be useful in the elderly, although further exploration is required.

Metabolic syndrome associated with toenail onychomycosis in Taiwanese with diabetes mellitus

BACKGROUND

Onychomycosis is a complication of diabetes mellitus (DM), which has a deleterious impact on the quality of life. Aim To explore the prevalence of onychomycosis amongst Taiwanese diabetics, and to analyze the factors associated with onychomycosis after adjusting for age and sex.

METHODS

A total of 1245 Taiwanese diabetics were enrolled, and a nested case-control study was performed by onychomycosis outcome and the exposures were compared.

RESULTS

The overall prevalence of onychomycosis among DM patients was 30.76% (383/1245), with a significantly higher prevalence in men than in women (P = 0.024). The factors associated with onychomycosis in matched pairs by gender and age were analyzed in 375 pairs. It was found that metabolic syndrome, obesity, triglyceride (TG) levels, and glycosylated hemoglobin (HbA1c) were associated with onychomycosis (P < 0.05).

CONCLUSION

Higher prevalence rates of onychomycosis were found in men and older DM patients. Metabolic syndrome, obesity, high TG levels, and poor glycemic control were associated with onychomycosis.

Insulin differentially regulates monocyte and polymorphonuclear neutrophil functions in healthy young and elderly humans

CONTEXT

Insulin can regulate immune cell function. Aging is associated with various degrees of insulin resistance together with reduced immune cell activity.

OBJECTIVE

We investigated the hypothesis that blood monocytes and polymorphonuclear neutrophils (PMNs) are less responsive to the action of insulin in elderly subjects. DESIGN-INTERVENTION: We evaluated the effect of hyperinsulinemia (0.7 mU/kg(-1) fat-free mass per minute(-1)) on monocyte and PMN activity using a 4-h euglycemic clamp technique.

PARTICIPANTS

Eight young (24 +/- 6 yr old) and nine elderly (69 +/- 4 yr old) healthy volunteers participated in the study.

MAIN OUTCOME MEASURES

Monocyte and PMN receptor expression and density were measured using flow cytometric detection. PMN chemotaxis toward formyl-Met-Leu-Phe (fMLP) was evaluated using a two-compartment chamber. PMN and monocyte phagocytosis was determined by measuring the engulfment of opsonized particles. Microbicidal functions were determined based on the production of reactive oxygen species (ROS) and bactericidal protein by stimulated cells.

RESULTS

The density of PMN and monocyte insulin receptors was not affected by age or insulin clamp treatment regardless of the age. Insulin was able to regulate the expression of receptors involved in PMN action in the young-adult group only. PMN chemotaxis was up-regulated by insulin in both groups. In contrast, although insulin stimulated phagocytosis and bactericidal activity in young-adult subjects, the ability of PMN to adapt to physiological hyperinsulinemia was blunted in the older group. The effect of insulin on monocyte bactericidal properties seemed to be limited, although a suppressive action on fMLP-induced ROS production was detected in young adults.

CONCLUSIONS

We confirmed the presence of the insulin receptor on monocyte and PMN membranes. We revealed that insulin has a limited action on monocyte function. Insulin has a priming effect on the main PMN functions. Immune cell function adapted poorly to insulin infusion in the elderly subjects.

Adverse effects of reactive oxygen species on vascular reactivity in insulin resistance

Insulin resistance (IR) has adverse effects on the reactivity of arteries and arterioles and promotes arterial hypertension and vascular occlusive diseases. Altered reactivity of resistance vessels occurs at both the endothelium and smooth-muscle levels. One major mechanism of vascular dysfunction with IR involves the augmented generation, availability, and/or actions of reactive oxygen species (ROS). Scavengers of ROS are able immediately to restore normal dilator responsiveness in arteries from IR animals. Other factors, such as increased importance of constrictor agents such as endothelin, also restrict normal dilator responses. The basis of ROS-mediated vascular dysfunction in IR may be secondary to underlying inflammatory processes throughout the arterial wall. Although ROS scavengers may be beneficial in the short term, prolonged treatments involving behavioral approaches, such as changes in diet, weight loss, and regular exercise, and pharmacological approaches, involving the use of insulin-sensitizing agents, inhibitors of the renin-angiotensin system, or administration of statins, appear to offer benefits against the detrimental vascular effects of IR. Nonetheless, the most effective approach appears to involve prevention of IR via adoption of a healthy lifestyle by young people.

Relationship between osteoporosis and cardiovascular disease in postmenopausal women

In the placebo group of the MORE study, including 2576 postmenopausal women (mean age, 66.5 years), the authors describe a strong linear association between the severity grade of osteoporosis (from low BMD to presence of severe vertebral fractures) and the future risk of cardiovascular events. Accordingly, treatment of postmenopausal osteoporosis should include consideration of measures to prevent adverse cardiovascular outcomes.

INTRODUCTION

Observations indicate an inverse association between BMD and the severity of peripheral atherosclerosis in postmenopausal women. The predictive value of osteoporosis and its different severity stages for the risk of acute cardiovascular events remains unknown.

MATERIALS AND METHODS

Participants were 2576 women (mean age, 66.5 years) assigned to placebo and followed for 4 years in an osteoporosis treatment trial. Those with at least one vertebral fracture or total hip BMD T score < or = -2.5 at baseline were defined as having osteoporosis, whereas those without vertebral fracture and total hip BMD T score between -2.5 and -1 were defined as having low bone mass. The primary outcome for these posthoc analyses was the incidence of adjudicated fatal or nonfatal cardiovascular events.

RESULTS

After adjustment for potential confounders, women with osteoporosis had a 3.9-fold (95% CI, 2.0-7.7; p < 0.001) increased risk for cardiovascular events compared with women with low bone mass. Under the same boundaries, a total hip BMD T score < or = -2.5 versus a T score between -2.5 and -1 was associated with a 2.1-fold (95% CI, 1.2-3.6; p < 0.01) increase in risk, whereas presence of at least one vertebral fracture versus no vertebral fracture at baseline was associated with a 3.0-fold (95% CI, 1.8-5.1; p < 0.001) increase in risk. The risk of cardiovascular events increased incrementally with the number and increasing severity of baseline vertebral fractures (both p < 0.001).

CONCLUSIONS

Postmenopausal women with osteoporosis are at an increased risk for cardiovascular events that is proportional to the severity of osteoporosis at the time of the diagnosis. Treatment of postmenopausal osteoporosis should include consideration of measures to prevent cardiovascular outcomes.

Novel associations between bioavailable estradiol and adipokines in elderly women with different phenotypes of obesity: implications for atherogenesis

BACKGROUND

Peripheral adiposity confers protection against diabetes and atherosclerosis in elderly women. The underlying mechanisms, however, remain to be elucidated.

METHODS AND RESULTS

On the basis on dual-energy X-ray absorptiometry measurements of central fat mass (CFM) and peripheral fat mass (PFM), we identified 290 elderly women with distinct forms of body fat distribution (lean, peripheral obesity, central obesity, or general obesity). Study parameters were plasma tumor necrosis factor-alpha, interleukin (IL)-6, adiponectin, estradiol, sex hormone-binding globulin, insulin resistance, and aortic calcification, graded on lateral radiography. In peripherally and generally obese women, plasma estradiol and insulin resistance were significantly lower, whereas sex hormone-binding globulin and adiponectin were significantly higher compared with centrally obese women independent of age, body mass index, total fat mass, and smoking habits (all P<0.05). After adjustment for these confounders, IL-6 in centrally obese women was comparable with that seen in generally obese (similar high CFM%) but significantly higher than in peripherally obese women and lean women (low CFM%). Atherosclerosis was less severe in generally obese (2.5+/-0.3) compared with centrally obese women (5.0+/-0.7, P=0.001). In multiple regression analysis, total fat mass, body fat distribution, insulin resistance, estradiol, current smoking, treated hyperlipidemia, and treated hypertension contributed independently to the variation of aortic calcification (R=0.55, SEE=3.60, P<0.001).

CONCLUSIONS

Abundant presence of PFM in generally obese women is associated with increased plasma adiponectin and higher insulin sensitivity, which could explain the apparent protection against the atherogenic effects of IL-6 derived from CFM. Low peripheral exposure to estradiol appears to be a sine qua non of maintained adiponectin secretion from PFM.