Biomedical subjects

A S Ryan

Publications and source records attributed to A S Ryan.

At least 37 records · Page 2Linked to original sources

PubMed1999

Formula tolerance in postbreastfed and exclusively formula-fed infants.

OBJECTIVE: Perceived intolerance to infant formula is a frequently reported reason for formula switching. Formula intolerance may be related to perceived symptoms of constipation, fussiness, abdominal cramps, and excessive spit-up or vomit. Commercially available formulas differ from each other in processing and in sources and levels of protein, lipids, and micronutrients. These differences may affect tolerance. The objective of this article was to compare the tolerance of two commercially available powder infant formulas that differ in composition. Measures of tolerance in exclusively breastfed infants weaned to an infant formula and exclusively formula-fed infants were evaluated. METHODS: Two clinical studies were conducted. In study 1, 82 healthy, full-term infants who were exclusively breastfed at the time of enrollment were randomized at weaning to formula A (commercially available Similac With Iron Powder) or formula B (previously available Enfamil With Iron Powder). Parents completed daily records of tolerance during exclusive breast milk feeding, during the weaning period, and for a 2-week exclusive formula-feeding period. In study 2, 87 healthy, full-term infants who were exclusively formula-fed at the time of study enrollment (by 2 weeks of age) were fed a standard cow milk-based formula (previously commercially available Similac With Iron Powder) and then randomized to receive formula A or B for a 2-week period. Parents completed daily records of tolerance throughout the study. Formula A was a cow milk-based formula with a whey:casein ratio of 48:52 and a fat blend of 42% high-oleic safflower, 30% coconut, and 28% soy oils. Formula B was a cow milk-based formula with a whey:casein ratio of 60:40 and a fat blend of 45% palm olein, 20% soy, 20% coconut, and 15% high-oleic sunflower oils. Both formulas had lactose as the source of carbohydrate and contained 12 mg of iron per liter. Only formula A contained nucleotides at the time of the study. Measures of tolerance included volume of each formula feeding, occurrences of spit-up and/or vomit, and the color (yellow, green, brown, or black) and consistency (water, loose/mushy, soft, formed, or hard) of each stool. RESULTS: In both studies, volume of formula intake, weight gain, and incidence of spit-up or vomit did not differ between feeding groups. In study 1, stool frequency decreased significantly from the exclusive breast milk period to weaning. Stools also became firmer as infants moved from breast milk to weaning and to exclusive formula feeding. When formula was introduced into the diet, stools became less yellow and more green. Infants weaned to formula B had less frequent stools, fewer brown stools, and more yellow stools than did infants fed formula A. In both studies, infants fed formula B experienced significantly firmer stools than did those fed formula A. CONCLUSIONS: The present clinical studies indicate that the composition and/or processing of milk-based powder iron-fortified infant formulas affect stool characteristics experienced by infants. The inclusion of palm olein oil in formula B may be the reason for the observed differences in stool characteristics. Palm olein is used in infant formulas to provide palmitic acid at a level similar to that found in breast milk. However, palmitic acid from palm olein is arranged differently from that in breast milk triglyceride and is poorly absorbed. Unabsorbed palmitic acid tends to react with calcium to form insoluble soaps, and the level of these soaps is correlated with stool hardness. The pattern of softer stools and greater frequency of stooling associated with formula A is similar to the stool pattern in the exclusively breastfed infant. Thus, the use of formula A may ease the transition from breast milk to formula feeding and ameliorate parents' perception that constipation is associated with iron-fortified formula.

Animals↗

PubMed1998

Resistive training maintains bone mineral density in postmenopausal women.

We examined the effects of a total body resistive training program (RT) on total and regional bone mineral density (BMD) in older women. Twenty-seven healthy postmenopausal women (mean age 62 +/- 1 years) participated in a strength training program three times/week for 16 weeks. Strength was assessed before and after training by either one or three repetition maximum (1RM and 3RM) tests. Both upper and lower body strength significantly increased by 36-65% and 32-98%, respectively, after training. There was a small but significant decrease in body weight and body mass index after training (P < 0. 05), with no change in the waist-to-hip ratio. BMD, assessed by dual-energy X-ray absorptiometry, did not change over the duration of the training period in the anterioposterior spine (L2-L4), femoral neck, Ward's triangle, and greater trochanter. BMD of the total body, lateral spine (B2-B4), and the regions of the radius (1/3 radius and ultradistal radius) also did not fall in subsets of these women. Muscular strength of both the leg and chest press were significantly associated with L2-L4, femoral neck, Ward's triangle, and greater trochanter BMD (range r = 0.57-0.84, all P < 0.005). Markers of bone turnover, namely, bone-specific alkaline phosphatase, osteocalcin, and urinary aminoterminal cross-linked telopeptide of type I collagen did not change significantly. In conclusion, a resistive training program maintains BMD and improves muscular strength in healthy, older women. This may be important in preventing the negative health outcomes associated with the age-related loss of bone density.

Aged↗

PubMed1998

Loss of bone mineral density in women athletes during aging.

Total and regional bone mineral density (BMD) by dual-energy-X-ray absorptiometry (DXA) and bone turnover were tested in 50 highly trained women athletes and 21 sedentary control women (18-69 years; BMI < 25 kg/m2). VO2max (ml . kg-1 . min-1) and lean tissue mass (DXA) were significantly higher in the athletes versus controls (both P < 0.0001). Total body BMD did not decline significantly with age in the athletes whereas lumbar spine (L2-L4) BMD approached statistical significance (r = -0.26; P = 0.07). Significant losses of the femoral neck (r = - 0.42), Ward's triangle (r = -0.53), and greater trochanter BMD (r = -0.33; all P < 0.05) occurred with age in the athletes. In the athletes, total body BMD, L2-L4 BMD, and BMD of all sites of the femur were associated with lean tissue mass (r = 0.32 to r = 0.57, all P < 0.05) and VO2max (r = 0.29 to r = 0.48, all P < 0.05). Femoral neck and greater trochanter BMD were higher in the athletes than in controls (both P < 0.05) and lumbar spine and Ward's triangle BMD approached statistical significance (both P = 0.07). Bone turnover was assessed by serum bone-specific alkaline phosphatase (B-ALP), urinary deoxypyridinoline cross-links (Dpd), and urinary aminoterminal cross-linked telopeptides (NTX). There were no relationships between B-ALP or Dpd with age whereas NTX increased with age (r = 0.46, P < 0.05) in the entire group. Levels of B-ALP and NTX were negatively associated with total body, L2-L4, femoral neck, Ward's triangle, and greater trochanter BMD (P < 0.05). B-ALP and Dpd were not significantly different between athletes and controls whereas NTX was lower in the athletes than in controls (P < 0.001). The high levels of physical activity observed in women athletes increase aerobic capacity and improve muscle mass but are not sufficient to prevent the loss of bone with aging.

Absorptiometry, Photon↗

PubMed1998

Acute and chronic resistive exercise increase urinary chromium excretion in men as measured with an enriched chromium stable isotope.

Both exercise and chromium exert beneficial effects on insulin function. The mechanism by which exercise improves insulin response may involve an alteration in Cr metabolism. To determine the effects of acute and chronic resistive exercise on urinary Cr losses, we measured the effects of acute resistive exercise and 16 wk of resistive exercise training on urinary Cr losses of 10 men 53-63 y of age. Subjects consumed diets in compliance with the American Heart Association Phase I diet with a Cr content of 30 +/- 4 microg/d. Sixteen weeks of resistive exercise training led to approximately 40% increases in upper and lower body strength, increases in fat-free mass and decreases in the percentage of body fat. An enriched stable isotope of Cr, 53Cr, was employed to differentiate the exogenously administered Cr from the native endogenous Cr. Both acute and chronic resistive exercise increased 53Cr losses. These data demonstrate that the improvements in body composition due to resistive exercise are associated with increased urinary Cr losses that are consistent with increased absorption.

Adipose Tissue↗

PubMed1998

Aerobic exercise maintains regional bone mineral density during weight loss in postmenopausal women.

This study examines the effects of weight loss by caloric restriction (WL) and aerobic exercise plus weight loss (AEx+WL) on total and regional bone mineral density (BMD) in older women. Healthy, postmenopausal women [age 63 +/- 1 (SE) yr] not on hormone-replacement therapy underwent 6 mo of WL (n = 15) consisting of dietary counseling one time per week with a caloric deficit (250-350 kcal/day) or AEx+WL (n = 15) consisting of treadmill exercise three times per week in addition to the weight loss. Maximal aerobic capacity increased only in the AEx+WL group (P < 0. 001). Body weight, percent fat, and fat mass decreased similarly in both groups (P < 0.005), with no changes in fat-free mass. Total body BMD (by dual-energy X-ray absorptiometry) decreased in both groups (P < 0.05). Femoral neck, Ward's triangle, and greater trochanter BMD decreased in the WL group (P </= 0.05) but were not significantly different after AEx+WL. L2-L4 BMD did not significantly change in either group. Thus WL and AEx+WL both result in losses of total body BMD; however, AEx+WL appears to prevent the loss in regional BMD seen with WL alone in healthy, older women. This suggests that the addition of exercise to weight-loss programs may reduce the risk for bone loss.

Aged↗

PubMed1998

Insulinotropic hormone glucagon-like peptide-1-(7-37) appears not to augment insulin-mediated glucose uptake in young men during euglycemia.

Glucagon-like peptide-1 (GLP-1) is an intestinal insulinotropic hormone that augments insulin secretion in response to meals and lowers blood glucose levels in both type 1 and type 2 diabetic subjects. It has been proposed that a substantial component of the glucose-lowering effects of GLP-1 occurs via insulin-independent mechanisms. However, the interpretations of the studies have been controversial. This study was conducted to examine whether glucagon-like peptide (GLP-1) has an insulin-like effect during euglycemia. Nine young lean men (age, 25 +/- 1.4 yr; body mass index, 24.0 +/- 0.7 kg/m2) volunteered to participate in two euglycemic clamp studies (n = 18 clamps) for 120 min. The initial clamp was performed with a primed continuous infusion of GLP-1 at a final rate of 1.5 pmol/kg.min from 0-60 min. At 60 min, the GLP-1 infusion was terminated, and euglycemia was maintained from 60-120 min. After the GLP-1 study, each individual's plasma insulin level was measured. A second study was performed that was identical to the first, with the infusion of regular insulin in place of GLP-1. Insulin infusion rates were designed in each individual to simulate plasma insulin levels produced during the GLP-1 infusion. The rate of disappearance of glucose was calculated for each subject. Basal plasma insulin levels were similar between studies and averaged 49 +/- 5 pmol/L. Basal GLP-1 levels were also similar (6.0 +/- 1.0 pmol/L). In response to the GLP-1 infusion, although basal plasma glucose levels were clamped, significant increases in insulin occurred in all subjects (P < 0.001). With the nearly identical plasma insulin levels during the two studies (30-60 min levels: GLP-1 study, 151 +/- 48; insulin study, 146 +/- 31 pmol/L), the rate of disappearance of glucose progressively increased in response to both GLP-1 and insulin infusions, but was not significantly different between the studies. The design of the study necessitated conducting the GLP-1 study first, which may have been accompanied by a greater stress than the second study. We, therefore, measured cortisol levels. Basal cortisol (and ACTH) levels were not different. However, cortisol levels significantly increased during the GLP-1 infusions, and this was preceded by an increase in ACTH levels. Somatostatin levels were not different either basally or during the clamps. We conclude that in the euglycemic state, an acute infusion of GLP-1 does not have insulin-like effects in lean nondiabetic men. Intravenous administration of GLP-1 activates hypothalamic neuroendocrine neurons.

Adrenocorticotropic Hormone↗

PubMed1998

The effect of age and glycemic level on the response of the beta-cell to glucose-dependent insulinotropic polypeptide and peripheral tissue sensitivity to endogenously released insulin.

Normal aging is characterized by a progressive impairment in glucose tolerance. An important mechanism underlying the glucose intolerance of aging is an impairment in glucose-induced insulin release. These studies were conducted to determine whether the age-related impairment in insulin release was caused by a decreased beta-cell sensitivity to glucose-dependent insulinotropic polypeptide (GIP). Thirty-one Caucasian men were divided into four groups: two young groups (age range: 19-26 yr, n = 15) and two old groups (age range: 67-79 yr, n = 16). Each volunteer participated in three studies (n = 93 clamps). Hyperglycemic clamps were conducted at two doses [basal plasma glucose (G) + 5.4 mmol/L and G + 12.8 mmol/L] for 120 min. In the initial hyperglycemic clamp, only glucose was infused. In subsequent studies, GIP was infused at a final rate of 2 or 4 pmol/ kg(-1) x min(-1) from 60-120 min. Basal plasma insulin and GIP levels were similar in the young (41 +/- 6 and 51 +/- 6 pmol/L) and the old subjects (42 +/- 6 and 66 +/- 12 pmol/L) in all studies. First- and second-phase insulin responses were similar during the control study and during the first 60 min of each GIP infusion study in both groups. The 90-120 min GIP values were similar between groups and between hyperglycemic plateaus during the 2 and 4 pmol/kg(-1) x min(-1) GIP infusion (young: 342 +/- 28 and 601 +/- 44 pmol/L, old: 387 +/- 45 and 568 +/- 49 pmol/L). In response to the GIP infusions, significant increases in insulin occurred in young and old at both glucose levels (P < 0.01). The potentiation of the insulin response caused by GIP was greater in the young subjects than in the old, in the G + 5.4 mmol/L studies (P < 0.05). However, the insulin response to GIP was similar in both young and old during the G + 12.8 mmol/L clamps. The insulinotropic effect of the incretin was higher in the young and in the old, in the G + 12.8 mmol clamps, than in the G + 5.4 mmol/L clamps. We conclude that normal aging is characterized by a decreased beta-cell sensitivity to GIP during modest hyperglycemia, which may explain, in part, the age-related impairment in glucose-induced insulin release. We also find that the insulinotropic effect of GIP is increased with increasing levels of hyperglycemia.

Adult↗

PubMed1997

Gender differences in the response of plasma leptin concentrations to weight loss in obese older individuals.

Plasma leptin concentration is directly related to the degree of obesity and is higher in women than in men of the same body mass index (BMI). We hypothesized that fasting plasma leptin concentrations and the response of leptin to weight loss would differ in older men and women of a similar fat mass. Plasma leptin concentrations (radioimmunoassay) and fat mass (DXA) were measured in 47 older, obese (BMI = 30 +/- 4 kg/m2) women and 23 older, obese (BMI = 31 +/- 3 kg/m2) men after a 2 to 4 week period of weight and dietary stabilization, and then in 22 of the women and 18 of the men after a 6-month weight loss intervention (250-350 kcal/d deficit). Leptin correlated with fat mass in men and women (r = 0.75 and r = 0.77, respectively; p values < 0.0001), but women had 3-fold higher leptin levels for a given fat mass than men (p = 0.01). In response to the 6-month hypocaloric diet, men and women lost a similar percentage of fat mass (-13% and -16%, respectively), but the relative decline in circulating leptin was greater in women than men (-45% and -21%, respectively; p < 0.0001). In addition, when leptin was normalized for fat mass using the ratio method, the decrease in leptin per kilogram of fat mass was greater in women than men (-0.37 +/- 0.34 vs. -0.04 +/- 0.06 ng/mL/kg; p < 0.01). After weight loss, the change in leptin concentrations correlated positively with the change in fat mass in men (r = 0.60; p < 0.01), but not in women (r = 0.31; p = 0.17). Furthermore, the loss in fat mass correlated negatively with baseline leptin levels in women (r = -0.47; p < 0.05), but not in men (r = 0.03, p = NS). These results indicate that the decline in leptin concentration with weight loss correlates with the loss in fat mass in men; but, in women, other factors affect the decrease in leptin concentration. This suggests that the role of leptin in the regulation of obesity is gender-specific and may account for gender differences in response to hypocaloric treatment and maintenance of lost weight.

Adipose Tissue↗

PubMed1997

Functions of dietitians providing nutrition support to patients with inherited metabolic disorders.

This article examines functions of dietitians who provide nutrition services to patients with inherited metabolic disorders. A survey questionnaire was developed and pilot-tested in a sample of dietitians, revised, and mailed to all dietitians in the United States who treat patients with inherited metabolic disorders. One hundred forty-two usable questionnaires were returned. Descriptive statistics were used to calculate response frequency. The highest academic degree attained by 37% of the dietitians was a bachelor's degree; 58% had earned a master's degree and 5% a doctorate. Dietitians provided nutrition services during diagnosis, critical illness, and long-term care. More than 90% of the dietitians performed these functions: evaluated nutrition status; prepared, implemented, and evaluated the nutritional support plan; revised the nutrition support plan as needed; monitored dietary compliance; coordinated care with other agencies; developed materials and educated parents, caregivers, and patients about the nutrition support plan; and recorded information in the medical record. Without nutrition support, patients with inherited metabolic disorders may become mentally retarded, experience neurologic or metabolic crises, or die.

Dietetics↗

PubMed1997

Plasma leptin concentrations and energy expenditure in heart failure patients.

Leptin, the protein encoded by the obese gene, is a newly described hormone implicated in the regulation of energy balance. To examine the possible role of leptin in the energy dysregulation that frequently accompanies chronic heart failure, we examined plasma leptin concentrations and energy expenditure in 18 heart failure patients (aged 71 +/- 6 years) and 46 healthy elderly controls (66 +/- 6 years). Plasma leptin concentrations were measured by radioimmunoassay, daily energy expenditure by doubly labeled water, and body composition by dual-energy x-ray absorptiometry. Fat mass was lower (P < .01) in heart failure patients compared with healthy controls, whereas fat-free mass did not differ between groups. Plasma leptin concentrations were not different between heart failure patients and healthy controls (5.1 +/- 4.2 v 6.8 +/- 4.4 pg/mL) and remained similar after statistical control for fat mass (6.0 +/- 3.1 v 7.1 +/- 3.2 pg/mL). Plasma leptin was related to fat mass in heart failure patients (r = .92, P < .01) and healthy controls (r = .69, P < .01). Free-living daily and physical-activity energy expenditures were lower (P < .01) in heart failure patients compared with healthy controls. Plasma leptin concentrations were related to both daily (r = .67, P < .01) and resting (r = .67, P < .01) energy expenditure in heart failure patients, but not in healthy controls (r = .09 and r = .33, respectively). In conclusion, we found an association between plasma leptin concentrations and energy expenditure in heart failure patients, but not in healthy controls. Thus, leptin may participate in the regulation of energy expenditure and body energy stores in heart failure patients.

Aged↗

PubMed1997

Increased disorderliness of basal insulin release, attenuated insulin secretory burst mass, and reduced ultradian rhythmicity of insulin secretion in older individuals.

Insulin is secreted in a pulsatile fashion. Rapid pulses are considered to be important for inhibiting hepatic glucose output, and ultradian pulses for stimulating peripheral glucose disposal. Aging is characterized by a progressive impairment in carbohydrate tolerance. We undertook the current studies to determine whether alterations in pulsatile insulin release accompany the age-related changes in carbohydrate metabolism. Healthy young (n = 8; body mass index, 21 +/- 1 kg/m2; age, 24 +/- 1 yr) and old (n = 9; body mass index, 24 +/- 1 kg/m2; age, 77 +/- 2 yr) volunteers underwent two studies. In the first study, insulin was sampled every 1 min for 150 min, and pulse analysis was conducted using a recently validated multiparameter deconvolution technique. In the second study, insulin was sampled every 10 min for 600 min, and insulin release was evaluated by Cluster analysis. In the 150-min studies, insulin secretory burst mass (P < 0.05) and amplitude (P < 0.01) were reduced in the elderly. In addition, approximate entropy, a measure of irregularity or disorderliness of insulin release, was increased in the aged (P < 0.01). In the 600-min studies, interpulse interval was greater in the aged (P < 0.05), and burst number was less (P < 0.05). We conclude that normal aging is characterized by more disorderly insulin release, a reduction in the amplitude and mass of rapid insulin pulses, and a decreased frequency of ultradian pulses. Whether these alterations in insulin pulsatility contribute directly to the age-related changes in carbohydrate metabolism will require further study.

Activity Cycles↗

PubMed1997

The resurgence of breastfeeding in the United States.

OBJECTIVE: To update reported rates of breastfeeding through 1995 and to compare rates in 1995 with those from 1989. METHODS: The Ross Laboratories Mothers' Survey, first conducted in 1955, is a large, national, mail survey designed to determine patterns of milk feeding to 6 months of age. Questionnaires are mailed to a representative sample of mothers when their infants are 6 months of age. In 1989, 196 000 questionnaires were mailed, and in 1995, 720 000 questionnaires were mailed. Mothers were asked to recall the type of milk fed to their infants immediately after birth, in the hospital, and during each of the first 6 months of age. The rates of breastfeeding in the hospital and at 6 months of age were evaluated. RESULTS: The Ross Laboratories Mothers' Survey demonstrates recent increases in both the initiation of breastfeeding and continued breastfeeding at 6 months of age. Comparing rates in 1989 and 1995, the initiation of breastfeeding increased more than 14% (from 52.2% to 59.7%). There was a 19.3% increase in the rate of breastfeeding at 6 months of age (from 18.1% to 21.6%). The increases in breastfeeding were observed across all sociodemographic groups but were greater among groups that have historically been less likely to practice breastfeeding: women who were black, younger (<25 years of age), in the lowest income group (<$10 000), no more than grade school educated, primiparous, and living in the South Atlantic region of the United States; women who had infants of low birth weight; women who were employed full time outside the home; and women who participated in the Women, Infants, and Children supplemental food program. Nevertheless, breastfeeding was most common in the western states and among women who were older, college educated, and multiparous, did not enroll in the Women, Infants, and Children program, were not employed outside the home, had infants of normal birth weight, and had higher disposable incomes. CONCLUSION: The sharp increase in rates of breastfeeding among groups that are less likely to breastfeed is encouraging. However, these groups are still the least likely to initiate breastfeeding. Educational efforts that extol positive attitudes about breastfeeding must be continued to support mothers who are young, poor, and less educated.

Adult↗

PubMed1996

Resistive training increases insulin action in postmenopausal women.

BACKGROUND: This study examined the effects of 4 months of resistive training in postmenopausal women on glucose metabolism and peripheral tissue sensitivity to endogenously released insulin. METHODS: Thirteen moderately obese (30-49% body fat) postmenopausal women (50-65 years) participated in the study. The six more obese women were enrolled in the resistive training with weight loss (RT & WL) program, while the remainder participated in resistive training alone (RT). beta-cell sensitivity to glucose and peripheral tissue sensitivity to endogenously released insulin were examined during hyperglycemic clamps (7.9 mmol/L above basal) before and after the intervention(s). RESULTS: The RT program resulted in a significant improvement in upper and lower body strength (p < .01) in all subjects. Body weight, fat mass, and percent body fat decreased with RT & WL (p < .001), but did not change with RT alone. There was no change in fat-free mass or maximal oxygen consumption after the intervention(s). Insulin response during the last 20 min of the 2 hr hyperglycemic clamps (7.9 mmol/L above basal plasma glucose levels) decreased after the intervention(s) in the entire group by 29% (p < .01), but decreased more in the group that lost weight (43%, p < .05) than in women who remained weight stable (16%, p = .05). Glucose utilization did not change. CONCLUSION: RT alone, or in combination with WL, increases insulin action and reduces hyperinsulinemia in postmenopausal women. This suggests that RT has the potential to ameliorate and perhaps prevent the development of insulin resistance and may reduce the risk for glucose intolerance and non-insulin-dependent diabetes mellitus (NIDDM) in postmenopausal women.

Aged↗

PubMed1996

A cross-sectional study on body composition and energy expenditure in women athletes during aging.

The relationships between total and regional body composition, intra-abdominal adipose tissue (IAAT), resting metabolic rate (RMR), and substrate oxidation were examined in 43 highly trained women athletes and 14 sedentary women aged 18-69 yr. Athletes were divided into four groups (18-29, 30-39, 40-49, and 50-69 yr) and controls into two groups (18-29 and 40-50 yr). Maximal oxygen consumption declined with age (r = -0.52, P < 0.0005) in the athletes and was higher in all groups of athletes than in controls (P < 0.0001). No differences in percent fat and fat-free mass (FFM) were found between the youngest and oldest athletes. Although body mass index was < 25 kg/m2 in all subjects, percent body fat and total fat mass were higher in controls than in athletes for both young and older women (all P < 0.05). FFM was higher in young athletes than in young controls (P < 0.0001). Despite similar percent fat among athletes, IAAT increased with age (r = 0.75, P < 0.0001), but subcutaneous abdominal fat and sagittal diameter did not. IAAT and subcutaneous abdominal fat were also higher in young controls than in young athletes and in older controls than in older athletes (all P < 0.005). Age and FFM were independent predictors of the decline in RMR in the athletes. Fat oxidation (g/day) was highest in the youngest athletes and declined with age (r = -0.47, P < 0.005). We conclude that intense chronic exercise in women athletes prevented the decline in FFM with age. Endurance-trained women have low IAAT stores, which may potentially reduce subsequent risk associated with the metabolic syndrome.

Adipose Tissue↗

PubMed1996

Pancreatic polypeptide administration improves abnormal glucose metabolism in patients with chronic pancreatitis.

Chronic pancreatitis (CP) is associated with lowered plasma levels and a blunted nutrient-induced release of pancreatic polypeptide (PP). To investigate the possible role of PP on glucose metabolism, we studied male patients with documented CP (n = 5) and obesity-matched control subjects (NL) (n = 6). Hepatic glucose production (HGP) and overall glucose disposal rates were determined by [3-3H]glucose infusion during a hyperinsulinemic-euglycemic clamp during three separate admissions. Basal rates of HGP were higher in CP patients. In response to an infusion of insulin (60 pmol.m-2.min-1), HGP fell 91 +/- 5% in NL subjects but only 68 +/- 8% in CP subjects (P < 0.05). One month later, the clamp was repeated during the final 2 h of an 8-h infusion of bovine PP (2 pmol.kg-1.min-1). HGP before the insulin infusion and its subsequent suppression (NL: 83 +/- 5%; CP: 86 +/- 15%) were nearly identical between groups. In follow-up studies 1 month after the PP infusion, HGP both basally and in response to insulin alone were similar to the first study. During oral glucose tolerance tests (OGTT) performed 18 h after the PP infusion, subjects with normal (n = 7) baseline OGTT responses showed no effect. All patients with diabetic (n = 3) or nondiagnostic (n = 1) OGTT responses, however, demonstrated lowered mean plasma glucose levels (approximately -2.3 mmol/L; range: -0.6 to -7.2 mmol/L). OGTTs repeated 1 month after the PP treatment showed a return to pretreatment responses. We conclude that chronic pancreatitis accompanied by PP deficiency is associated with partial hepatic resistance both in the basal state and in response to hyperinsulinemia. This impairment is reversed after iv PP administration. PP deficiency may therefore play a role in the development of pancreatogenic diabetes caused by pancreatic injury.

Adult↗

PubMed1996

The effects of acute hyperglycemia and hyperinsulinemia on plasma leptin levels: its relationships with body fat, visceral adiposity, and age in women.

The acute effects of hyperglycemia and hyperinsulinemia on plasma leptin levels were determined in 42 highly trained women athletes (18-69 yr) and 14 sedentary control women (18-50 yr, body mass index < 25 kg/m2), using the glucose clamp technique. The relationships of body composition, physical fitness, age, and plasma leptin levels were examined in all participants. In addition, the effect of weight loss and aerobic exercise and plasma leptin levels were examined in 4 Newly diagnosed untreated noninsulin-dependent diabetes mellitus patients. The time course of plasma leptin levels changed little from basal during hyperglycemic (approximately 10 mmol/L) or hyperinsulinemic-euglycemic (400-3000 pmol/L) clamp studies in either athletes, controls, or noninsulin-dependent diabetes mellitus patients. A strong correlation between plasma leptin levels and fasting insulin was present (r = 0.60, P < 0.001). Plasma leptin and percent fat were higher in controls than athletes (12.6 vs. 4.0 ng/mL and 33.2 vs. 20.8%; both P < 0.001). The relationships between percent fat (dual-energy x-ray absorptiometry) or intraabdominal adipose tissue (computed tomography) and leptin for the entire group were highly significant (r = 0.70, r = 0.52; P < 0.001). When percent fat was controlled, the relationship between fasting insulin and leptin remained (P < 0.002). There was not a significant association between age and plasma leptin levels in a univariate analysis in this population. However, after adjustment for percent fat, a significant inverse relationship between age and leptin appeared (P < 0.05). The weight loss and aerobic exercise program resulted in an average 6 +/- 0.8 kg wt loss. Leptin levels decreased > 28% in each patient (P < 0.01). In conclusion, neither acute hyperglycemia or hyperinsulinemia affects plasma leptin levels. Percent fat is the strongest predictor of leptin levels, even in lean, highly trained women athletes.

Adipose Tissue↗

PubMed1995

Resistive training increases fat-free mass and maintains RMR despite weight loss in postmenopausal women.

Percent body fat increases with age and is often accompanied by a loss in muscle mass, strength, and energy expenditure. The effects of 16 wk of resistive training (RT) alone or with weight loss (RTWL) on strength (isokinetic dynamometer), body composition (dual-energy X-ray absorptiometry), resting metabolic rate (RMR) (indirect calorimetry), and sympathetic nervous system activity (catecholamines) were examined in 15 postmenopausal women (50-69 yr). RT resulted in significant improvements in upper and lower body strength in both groups (P < 0.01). The nonobese women in the RT group (n = 8) did not change their body weight or fat mass with training. In the obese RTWL group (n = 7), body weight, fat mass, and percent body fat were significantly decreased (P < 0.001). Fat-free mass and RMR significantly increased with training in both groups combined (P < 0.05). There were no significant changes in resting arterialized plasma norepinephrine or epinephrine levels in either group with training. RT increases strength with and without weight loss. Furthermore, RT and RTWL increase fat-free mass and RMR and decrease percent fat in postmenopausal women. Thus, RT may be a valuable component of an integrated weight management program in postmenopausal women.

Aged↗

PubMed1994

Effects of strength training on total and regional body composition in older men.

The effects of a 16-wk strength-training program on total and regional body composition were assessed by dual-energy X-ray absorptiometry (DEXA), magnetic resonance imaging (MRI), and hydrodensitometry in 13 untrained healthy men [60 +/- 4 (SD) yr]. Nine additional men (62 +/- 6 yr) served as inactive controls. The strength-training program resulted in substantial increases in both upper (39 +/- 8%; P < 0.001) and lower (42 +/- 14%; P < 0.001) body strength. Total fat-free mass (FFM) increased by 2 kg (62.0 +/- 7.1 to 64.0 +/- 7.2 kg; P < 0.001), and total fat mass decreased by the same amount (23.8 +/- 6.7 to 21.8 +/- 6.0 kg; P < 0.001) when measured by DEXA. When measured by hydrodensitometry, similar increases in FFM (61.3 +/- 7.8 to 63.0 +/- 7.6 kg; P < 0.01) and decreases in fat mass (23.8 +/- 7.9 to 22.1 +/- 7.7 kg; P < 0.001) were observed. When measured by DEXA, FFM was increased in the arms (6.045 +/- 0.860 to 6.418 +/- 0.803 kg; P < 0.01), legs (19.416 +/- 2.228 to 20.131 +/- 2.303 kg; P < 0.001), and trunk (29.229 +/- 4.108 to 30.134 +/- 4.184 kg; P < 0.01), whereas fat mass was reduced in the arms (2.383 +/- 0.830 to 2.128 +/- 0.714 kg; P < 0.01), legs (7.583 +/- 1.675 to 6.945 +/- 1.551 kg; P < 0.001), and trunk (12.216 +/- 4.143 to 11.281 +/- 3.653 kg; P < 0.01) as a result of training.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗