Longitudinal functional recovery after geriatric cardiac surgery.

BACKGROUND: Impaired functional and cognitive status is an important outcome for older adults undergoing major cardiac surgery. We conducted this pilot study to gauge feasibility of assessing these outcomes longitudinally, from preoperatively up to two time points postoperatively to assess for recovery. METHODS: We interviewed patients aged ≥ 65 y preoperatively and repeated functional and cognitive assessments at 4-6 wk and 4-6 mo postoperatively. Simple unadjusted linear regression was used to test whether baseline measures changed at each follow-up time point. Then we used a longitudinal model to predict postoperative recovery overall, adjusting for comorbidity. RESULTS: A total of 62 patients (age 74.7 ± 5.9) underwent scheduled cardiac surgery. Preoperative activities of daily living (ADL) impairment was associated with poorer functional recovery at 4-6 wk postoperatively with each baseline ADL impairment conferring recovery of 0.5 fewer ADLs (P < 0.05). By 4-6 mo, we could no longer detect a difference in recovery. Preoperative cognition and physical activity were not associated with postoperative changes in these domains. CONCLUSIONS: A preoperative and postoperative evaluation of function and cognition was integrated into the surgical care of older patients. Preoperative impairments in ADLs may be a means to identify patients who might benefit from careful postoperative planning, especially in terms of assistance with self-care during the first 4-6 wk after cardiac surgery.

Short-term exercise improves beta-cell function and insulin resistance in older people with impaired glucose tolerance.

BACKGROUND: There is a high prevalence of diabetes and impaired glucose tolerance (IGT) in the older population. Normal aging is associated with insulin resistance and impaired insulin secretion, with greater defects in people with IGT. Short-term exercise has been found to increase insulin sensitivity, but little is known about acute exercise effects on beta-cell function in older people with IGT. METHODS: We assessed the effects of 7 consecutive days of supervised aerobic exercise (1 h/d at 60-70% heart rate reserve) in 12 sedentary older people with IGT. Screening included oral glucose tolerance test, stress/maximal O(2) uptake test, and dual-energy x-ray absorptiometry scan. Participants had a frequently sampled iv glucose tolerance test at baseline and 15-20 h after the seventh exercise session. Insulin sensitivity (S(I)), glucose disappearance constant (Kg, a measure of iv glucose tolerance), acute insulin response to glucose (AIRg), and disposition index (AIRg x S(I)), a measure of beta-cell function in relation to insulin resistance, were calculated. RESULTS: Exercise was well tolerated. Body weight, fasting glucose, fasting insulin, and iv glucose tolerance were unchanged with exercise. S(I) increased by 59%, AIRg decreased by 12%, and disposition index increased by 31%. There was no significant change in fasting lipid, catecholamine, leptin, or adiponectin levels. CONCLUSIONS: Short-term exercise not only improved insulin resistance but also significantly enhanced beta-cell function in older people with IGT. These effects of short-term exercise on beta-cell function cannot be explained by changes in body weight or circulating levels of lipids, leptin, adiponectin, or catecholamines.

Impaired beta-cell function in human aging: response to nicotinic acid-induced insulin resistance.

CONTEXT: Glucose tolerance declines with age and may involve impaired beta-cell sensitivity to glucose and beta-cell compensation for insulin resistance. OBJECTIVE: We investigated beta-cell sensitivity to glucose and beta-cell compensation for nicotinic acid-induced insulin resistance in young (age <35 yr) people with normal glucose tolerance (NGT) and old (age >60 yr) people with NGT and impaired glucose tolerance (IGT). DESIGN/PATIENTS/SETTING/INTERVENTION: Fifteen young NGT, 16 old NGT, and 14 old IGT were randomized to 2-wk treatment with nicotinic acid or placebo in a double-blind, crossover study in a university medical setting. At the end of each treatment period, participants had a frequently sampled iv glucose tolerance test and ramp clamp, in which insulin secretion rates (ISR) were determined in response to a matched 5-10 mm glucose stimulus. MAIN OUTCOME MEASURES: Insulin sensitivity (S(I)), acute insulin response to iv glucose (AIRg), and disposition index (AIRg x S(I), or beta-cell compensation for insulin resistance) from frequently sampled iv glucose tolerance testing, and ISR area under the curve (or beta-cell sensitivity to glucose) from ramp clamp were determined. RESULTS: Progressive impairments in insulin secretion as assessed by AIRg, disposition index, and ISR area under the curve were identified in older people with NGT, with more marked defects in older people with IGT. Nicotinic acid treatment significantly reduced S(I) in all groups. beta-Cell compensation for nicotinic acid-induced insulin resistance was incomplete in all three groups, with greater defects in the two older groups. CONCLUSIONS: Human aging is associated with impaired beta-cell sensitivity to glucose and impaired beta-cell compensation to insulin resistance.

Limitation of the homeostasis model assessment to predict insulin resistance and beta-cell dysfunction in older people.

CONTEXT: Studies in older people have shown inconsistent agreement between homeostasis model assessment of insulin resistance (HOMA-IR) and dynamic measures of insulin action and have not evaluated HOMA beta-cell. OBJECTIVE: We compared measures of insulin sensitivity and beta-cell function from the frequently sampled iv glucose tolerance test (FSIGT) to HOMA models. DESIGN/PATIENTS/SETTING/INTERVENTION: Two hundred fourteen young and old with normal glucose tolerance (NGT) and old with impaired glucose tolerance (IGT) participated in a retrospective analysis of FSIGT data in a university medical setting. MAIN OUTCOME MEASURE: Sensitivity to insulin (S(I)) and acute insulin response to glucose (AIRg) from FSIGT were compared with HOMA models. RESULTS: S(I) and HOMA-IR measures identified similar patterns of increasing insulin resistance in the two older groups, compared with younger people with NGT, with the greatest degree of insulin resistance in older people with IGT (P < 0.05 vs. young and old NGT for both S(I) and HOMA-IR). Agreement between HOMA-IR and S(I) was moderate (weighted kappa = 0.51). AIRg was similar in young and old NGT but was markedly decreased in old IGT (P < 0.05 vs. young and old NGT). HOMA-beta-cell was similar in the three groups. Agreement between HOMA beta-cell and AIRg was weak (weighted kappa = 0.35). CONCLUSIONS: HOMA-IR may detect age-related insulin resistance when comparing large populations of older people. However, dynamic testing appears to be necessary to quantitate diminished insulin secretion in older people.

Effect of lowering postprandial hyperglycemia on insulin secretion in older people with impaired glucose tolerance.

Glucose tolerance declines with age, resulting in a high prevalence of diabetes and impaired glucose tolerance (IGT) in the older population. Hyperglycemia per se can lead to impaired beta-cell function (glucose toxicity). We tested the role of glucose toxicity in age-related beta-cell dysfunction in older people (65 +/- 8 yr) with IGT treated with the alpha-glucosidase inhibitor acarbose (n = 14) or placebo (n = 13) for 6 wk in a randomized, double-blind study. Baseline and posttreatment studies included 1) an oral glucose tolerance test (OGTT), 2) 1-h postprandial glucose monitoring, 3) a frequently sampled intravenous glucose tolerance test (insulin sensitivity, or S(I)), and 4) glucose ramp clamp (insulin secretion rates, or ISR), in which a variable glucose infusion increases plasma glucose from 5 to 10 mM. The treatment groups had similar baseline body mass index; fasting, 2-h OGTT, and 1-h postprandial glucose levels; and S(I). In these carefully matched older people with IGT, both fasting (5.7 +/- 0.2 vs. 6.3 +/- 0.2 mM, P = 0.002) and 1-h postprandial glucose levels (6.9 +/- 0.3 vs. 8.2 +/- 0.4 mM, P = 0.02) were significantly lower in the acarbose than in the placebo group. Despite this reduction of chronic hyperglycemia in the acarbose vs. placebo group, measures of insulin secretion (ISR area under the curve: 728 +/- 55 vs. 835 +/- 81 pmol/kg, P = 0.9) and acute insulin response to intravenous glucose (329 +/- 67 vs. 301 +/- 54 pM, P = 0.4) remained unchanged and impaired. Thus short-term improvement of chronic hyperglycemia does not reverse beta-cell dysfunction in older people with IGT.

The GLP-1 derivative NN2211 restores beta-cell sensitivity to glucose in type 2 diabetic patients after a single dose.

Glucagon-like peptide 1 (GLP-1) stimulates insulin secretion in a glucose-dependent manner, but its short half-life limits its therapeutic potential. We tested NN2211, a long-acting GLP-1 derivative, in 10 subjects with type 2 diabetes (means +/- SD: age 63 +/- 8 years, BMI 30.1 +/- 4.2 kg/m(2), HbA(1c) 6.5 +/- 0.8%) in a randomized, double-blind, placebo-controlled, crossover study. A single injection (7.5 micro g/kg) of NN2211 or placebo was administered 9 h before the study. beta-cell sensitivity was assessed by a graded glucose infusion protocol, with glucose levels matched over the 5-12 mmol/l range. Insulin secretion rates (ISRs) were estimated by deconvolution of C-peptide levels. Findings were compared with those in 10 nondiabetic volunteers during the same glucose infusion protocol. In type 2 diabetic subjects, NN2211, in comparison with placebo, increased insulin and C-peptide levels, the ISR area under the curve (AUC) (1,130 +/- 150 vs. 668 +/- 106 pmol/kg; P < 0.001), and the slope of ISR versus plasma glucose (1.26 +/- 0.36 vs. 0.54 +/- 0.18 pmol x l[min(-1) x mmol(-1) x kg(-1)]; P < 0.014), with values similar to those of nondiabetic control subjects (ISR AUC 1,206 +/- 99; slope of ISR versus plasma glucose, 1.44 +/- 0.18). The long-acting GLP-1 derivative, NN2211, restored beta-cell responsiveness to physiological hyperglycemia in type 2 diabetic subjects.