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Biomedical subjects

D Elahi

Publications and source records attributed to D Elahi.

At least 91 records · Page 5Linked to original sources
PubMed1988

Somatostatin enhances insulin-mediated glucose disposal in elderly subjects.

Somatostatin (SRIH) infusion has been widely used in metabolic studies of carbohydrate metabolism. While the effects of SRIH itself on various aspects of carbohydrate economy have been assessed in young adults, such studies have not been conducted in the elderly, which represent an increasingly important study group. To examine the effect of SRIH on insulin-mediated glucose disposal in the elderly, we studied 12 (7 men and 5 women) healthy nonobese subjects, aged 65-80 yr. Paired 3-h euglycemic insulin clamp studies were performed in random order employing insulin alone (22 mU/m2.min) or insulin with SRIH (250 micrograms/h) and glucagon (0.4 ng/kg.min) to maintain normal basal plasma glucagon levels. Basal plasma insulin, glucose, glucagon, GH, and glucose production and disappearance were similar on each occasion. Steady state (10-180 min) mean plasma insulin [insulin alone, 298 +/- 12 (+/- SE); insulin; glucagon, and SRIH, 304 +/- 15 pmol/L] and glucagon (insulin alone, 85 +/- 7; insulin, glucagon, and SRIH, 96 +/- 9 ng/L) concentrations were similar. At steady state (150-180 min) glucose production was suppressed to similar levels (insulin alone, 26 +/- 7; insulin, glucagon, and SRIH, 36 +/- 13 mumol/kg.min). However, steady state glucose disposal was significantly higher during the SRIH infusion (insulin alone, 295 +/- 26; insulin, glucagon, and SRIH, 346 +/- 32 mumol/kg.min; P less than 0.02). We conclude that SRIH augments insulin-mediated glucose disposal in healthy older subjects at physiological levels of insulin.

Age Factors↗
PubMed1988

Reversal of abnormal glucose production after pancreatic resection by pancreatic polypeptide administration in man.

Pancreatic polypeptide (PP) deficiency has been associated with impaired hepatic sensitivity to insulin and pancreatogenic diabetes in chronic pancreatitis. Since pancreatic resection might also result in PP deficiency, hepatic responses to insulin infusion (0.25 mU/kg/min) were determined by the euglycemic glucose clamp technique in 10 patients who had previously undergone pancreatic resection for trauma and in eight healthy control subjects. Six resection patients (RES-PP) demonstrated deficient PP levels, with a mean increase of plasma immunoreactive PP of 20 +/- 7 pg/ml above basal rate after a test meal compared with 232 +/- 82 pg/ml in control subjects (p less than 0.01) and 353 +/- 133 pg/ml in four other patients undergoing resection with normal levels of immunoreactive PP (RES + PP) (p less than 0.03). Three identical insulin infusion studies were performed in each subject, the second of which was performed during the final 2 hours of an 8-hour infusion of bovine PP (2.0 pmol/kg/min). Whereas hepatic glucose production (HGP) in control subjects fell 74% +/- 4% from a basal rate of 2.0 +/- 0.1 mg/kg/min to a 60- to 120-minute value of 0.5 +/- 0.1 mg/kg/min during insulin infusion, HGP was suppressed only 58% +/- 5% in RES-PP subjects, from 1.9 +/- 0.1 to 0.8 +/- 0.1 mg/kg/min (p less than 0.05 vs controls). Intravenous infusion of PP corrected the hepatic resistance to insulin seen in the PP-deficient group. During PP infusion, HGP was suppressed 74% +/- 5% in RES-PP subjects, from 2.1 +/- 0.2 to 0.5 +/- 0.1 mg/kg/min (p less than 0.04 compared with initial study). PP infusion produced no significant change in glucose metabolism in control and RES + PP subjects. Overall glucose disposal rates were not altered by PP infusion in any group. These findings support a role of PP as a glucoregulatory hormone and suggest that PP deficiency may serve as a reversible pathophysiologic factor in the abnormal glucose metabolism seen after pancreatic resection.

Adult↗
PubMed1987

Splanchnic neural regulation of insulin and glucagon secretion in the isolated perfused human pancreas.

The isolated perfused human pancreas was employed as a model in which electrical stimulation of the celiac mixed neural bundle was performed in the presence or absence of selective neural blockers. The insulin and glucagon responses to hyperglycemia alone or in the presence of splanchnic nerve stimulation were similar in magnitude to the results obtained in a preliminary report on isolated human pancreatic function and in studies using animal models. Stimulation of the celiac neural bundle in the presence of hyperglycemia resulted in an inhibition of insulin release and in an augmentation of glucagon release. alpha-adrenergic stimulation resulted in a strong suppression of insulin secretion and a mild suppression of glucagon secretion. beta-adrenergic fiber stimulation caused a mild augmentation of both insulin and glucagon release, whereas the cholinergic fibers strongly stimulated both alpha- and beta-cell secretion. The predominant effects of celiac neural bundle stimulation are insulin inhibition by was of an alpha-adrenergic effect and glucagon stimulation by way of a cholinergic effect. Thus, in this in vitro human model, our data confirm that the splanchnic innervation of the pancreas has a potent regulatory role on pancreatic hormone release in human subjects.

Adolescent↗
PubMed1987

Insulin action in aging man: evidence for tissue-specific differences at low physiologic insulin levels.

This study examined the effect of age on insulin action in several tissues. Euglycemic insulin clamp studies were performed on healthy young (n = 7, 20 to 35 years, 10 and 20 mU/m2 X min insulin infusions) and old (n = 7, 66 to 80 years, 8 and 16 mU/m2 X min insulin infusions) adults. Insulin values were similar during both the lower (young, 24 +/- 1.6, old, 24 +/- 2.1 microU/ml) and higher (young, 40 +/- 3.3; old, 39 +/- 3.8 microU/ml) insulin infusion rates. Although suppression of hepatic glucose output (HGO) was more rapid (p less than .05) in the elderly group at each dose, HGO was eventually suppressed to similar levels in both age groups (low dose: young, 34.4 +/- 10.8, old, 25.3 +/- 1.8 mg/m2 X min; higher dose: young, 22.8 +/- 10.2, old, 6.2 +/- 2.1 mg/m2 X min). Glucose disposal was less (p less than .01) in the aged group at both insulin infusion rates. Suppression of C-peptide was slower in the elderly participants (p less than .05) in the low dose study. Suppression of free fatty acid and glucagon levels was the same in each age group. We concluded that the insulin resistance of aging is not generalized to all tissues.

Adult↗
PubMed1987

Somatostatin does not alter insulin-mediated glucose disposal.

We examined the effect of somatostatin (SRIH) infusion on insulin-mediated glucose disposal (Rd) in normal young subjects (n = 8) to determine the influence of SRIH on insulin action. Paired 3-h euglycemic insulin clamp studies were performed in random order employing insulin alone (25 mU/m2 X min) or insulin with SRIH (250 micrograms/h) and replacement of basal glucagon (0.4 ng/kg X min). Basal plasma glucose, insulin, glucagon (IRG), and GH concentrations, hepatic glucose production, and Rd were similar on each occasion. Steady state (10-180 min) plasma insulin insulin alone, 283 +/- 10 (+/- SEM); insulin, IRG, and SRIH, 284 +/- 10 pmol/L) and glucagon levels (insulin alone, 84 +/- 7; insulin, IRG, and SRIH, 82 +/- 7 ng/L) were similar. Hepatic glucose production (insulin alone, 0.66 +/- 0.12; insulin, IRG, and SRIH, 0.78 +/- 0.48 mg/kg X min) and Rd (insulin alone, 8.16 +/- 0.62; insulin, IRG, and SRIH, 8.17 +/- 0.61 mg/kg X min) were not different at steady state. We conclude that SRIH infusion with glucagon replacement does not augment insulin-mediated glucose disposal in normal young subjects at physiological insulin levels.

Adult↗
PubMed1986

Reversal of abnormal glucose metabolism in chronic pancreatitis by administration of pancreatic polypeptide.

Chronic pancreatitis, induced in dogs by pancreatic duct ligation, is associated with glucose intolerance due to insulin deficiency, reduced hepatic sensitivity to insulin, and a marked deficiency of pancreatic polypeptide. Treatment with a 14 day continuous subcutaneous infusion of pancreatic polypeptide resulted in improved oral glucose tolerance and improved hepatic glucose responses to insulin in dogs with chronic pancreatitis. No effect of continuous subcutaneous infusion of pancreatic polypeptide was seen in the control dogs. The time course of the effect of continuous subcutaneous infusion on the hepatic response to insulin was relatively immediate, whereas the effects on improvement in oral glucose tolerance were prolonged. We conclude that pancreatic polypeptide may function physiologically to enhance the hepatic glucose response to insulin and that alterations in glucose metabolism seen in chronic pancreatitis may be due, in part, to a deficiency in pancreatic polypeptide. Since treatment with continuous subcutaneous infusion of pancreatic polypeptide restored the hepatic response to insulin and oral glucose tolerance to more normal levels in our animal model, administration of pancreatic polypeptide may play a therapeutic role in the treatment of certain forms of pancreatogenic diabetes.

Animals↗
PubMed1986

The dawn phenomenon does not occur in normal elderly subjects.

To determine whether the dawn phenomenon occurs in normal elderly subjects and thus contributes to the progressive mild fasting hyperglycemia of aging, we examined the effect of physiological insulin levels on glucose disposal and hepatic glucose production (HGO) between 0530 and 0800 h, and 0930 and 1200 h. Paired euglycemic insulin clamp studies (8 mU/m2 X min) were performed on healthy old subjects (n = 5), employing [3H]glucose methodology to measure glucose production and disposal rates. Basal plasma insulin, GH, glucagon, and cortisol levels, and HGO and glucose disposal rates were similar before each study. Steady state plasma insulin values were slightly, but not significantly, lower during the dawn study [dawn: 20.3 +/- 1.1 (SE); control: 23.5 +/- 2.1 microU/ml, P = 0.08]. Insulin clearance rates were higher during the dawn study (dawn: 523 +/- 16; control: 430 +/- 19 ml/m2 X min, P less than 0.01). Maximum glucose disposal rates (dawn: 3.10 +/- 0.24; control: 3.03 +/- 0.23 mg/kg X min) and minimum HGO levels (dawn: 0.83 +/- 0.09; control: 0.62 +/- 0.03 mg/kg X min) were not significantly different in each part of the study. There was a significant decrease in plasma GH during the dawn (P less than 0.01, analysis of variance) but not the control studies. There was no difference in cortisol levels during the euglycemic clamp between the dawn and control studies. The mean decrement in glucagon during the insulin infusion was similar in each part of the study. We conclude that the dawn phenomenon does not occur in healthy elderly subjects despite an increase in insulin clearance during the dawn period.

Aged↗
PubMed1985

Glucose metabolism in glucose-intolerant older people during chromium supplementation.

The effects of chromic chloride (CrCl3) administered orally for 12 weeks to five elderly subjects with glucose intolerance were assessed. Pretreatment and posttreatment, the hyperglycemic clamp technique was employed to determine glucose utilization, beta-cell sensitivity to glucose, and tissue sensitivity to insulin. In addition, erythrocyte insulin binding was studied. Urinary chromium excretion increased approximately 5 fold indicating good compliance with supplementation. The oral glucose tolerance curves following supplementation were lowered from 60 to 120 minutes but only the 60-minute values were significantly lowered. In agreement with this was significantly increased glucose utilization during the hyperglycemic clamp studies. Tissue sensitivity to insulin, receptor affinity, and total insulin binding were unchanged by supplementation while beta-cell sensitivity to glucose increased following supplementation (P less than 0.04), and explained the increased glucose utilization. HDL and LDL and total cholesterol levels were slightly lower after chromium supplementation, but no change reached statistical significance. The LDL/HDL cholesterol ratio was unchanged. This study shows small but statistically significant effects of CrCl3 on carbohydrate metabolism. The clinical relevance of these effects, that is, their prophylactic or therapeutic significance, remains to be determined.

Aged↗
PubMed1985

The effect of age and glucose concentration on insulin secretion by the isolated perfused rat pancreas.

Age changes in the beta-cell's sensitivity to glucose as well as in its overall capacity to secrete insulin may play a part in the glucose intolerance of aging. The isolated perfused rat pancreas preparation was used to study the effect of age and glucose level on insulin secretion. Overnight-fasted male Wistar 12- and 23-month-old rats had basal plasma glucose levels of 106 +/- 4 (SE) and 100 +/- 4 mg/dl. Perfusate glucose levels were raised from 80 mg/dl to either 150, 220, or 360 mg/dl for 50 min (n = 6 to 8 in each group). Insulin secretion followed the typical biphasic pattern of an early spike and fall, followed by a sustained gradual increase at both ages. First-phase (0-10 min) insulin secretion in the old rats was significantly lower at 150 (184 vs. 524 microU/min, P less than 0.05) and 220 mg/dl (327 vs. 644 microU/min, P less than 0.05), while it was nearly identical at 360 mg/dl. Although lower in the old rats, second-phase (11-50 min) insulin secretion was not statistically significantly different for each glucose level. When first- and second-phase insulin secretion rates were combined, the old rats' insulin secretion was only lower at the 150 mg/dl level (248 vs. 426 microU/min, P less than 0.05). Thus, at the more physiological glucose level, old rats showed a significantly lower response, while at the higher levels insulin secretion was similar. This diminishing age effect with increasing glucose dose suggests a defect in islet sensitivity to glucose rather than a diminished capacity to secrete insulin.

Aging↗
PubMed1985

Impact of age on weight goals.

Although the health hazards due to excessive obesity and excessive leanness are multiple and diverse, weight recommendations for over 40 years have been based solely on the risk of dying. The weight recommendation tables in nearly universal usage have been derived from the experience of the life insurance industry. Those tables have not recommended any weight adjustments for age. An analysis of the actuarial data on which the most recent tables are based shows that minimal mortality occurs at progressively increasing body weight as age advances (20 to 29, through 60 to 69 years). There is, furthermore, no systematic sex difference in those weights. We have prepared height-weight tables that are age-specific and delete sex and body frame type as variables. These weight standards are lower for young adults and higher for older adults than those previously recommended. A review of 23 other reported populations confirms the need to adjust weight standards for age.

Actuarial Analysis↗
PubMed1984

The enteric enhancement of glucose-stimulated insulin release. The role of GIP in aging, obesity, and non-insulin-dependent diabetes mellitus.

The effect of aging, obesity, and non-insulin-dependent diabetes mellitus on glucose-stimulated gastric inhibitory polypeptide (GIP) levels was studied in 55 male subjects, ranging in age from 19 to 84 yr, and in obesity, expressed as body mass index, from 21 to 34. Studies were performed using the hyperglycemic glucose clamp technique, in which the blood glucose was maintained at 125 mg/dl above basal for 2 h. Glucose (40 g/m2 body surface) was ingested at 60 min. Plasma immunoreactive GIP (IR-GIP) did not change during intravenous (i.v.) glucose alone, but began to rise within 10 min after glucose ingestion and reached a peak at 30-40 min. Basal and stimulated IR-GIP levels were markedly elevated in diabetic subjects and modestly elevated in obese subjects, compared with appropriately matched controls. In contrast, age had little effect on plasma IR-GIP levels either in the basal state or after glucose ingestion. When IR-GIP responses to oral glucose were expressed as a relative change from basal levels, IR-GIP rose 86% in diabetic subjects and 243% in obese subjects, compared with 185% and 165% in their respective controls. IR-GIP rose 179% in young subjects and 144% in middle-aged subjects, while, in old subjects, the increase was 265%. Plasma IRI levels were reduced in the diabetic subjects, slightly elevated in obese subjects, and were similar in older and younger subjects. Beta cell sensitivity to endogenous GIP decreases with age, and is unchanged in both obesity and nonmedicated diabetes.

Adult↗
PubMed1983

A longitudinal study of nutritional intake in men.

Seven-day dietary diaries were provided by 180 male participants in the Baltimore Longitudinal Study of Aging during each of three time periods (1961 to 1965, 1966 to 1970, and 1971 to 1975). These men are a highly educated, upper-middle class group. At the time of their first diary, they were aged 35 to 74 years. The data were analyzed for aging, cohort, and time effects on diet by utilizing three types of research designs concurrently: cross-sectional, longitudinal, and time series. The nutrients considered were calories, protein, carbohydrate, fat, saturated fatty acids, polyunsaturated fatty acids, and cholesterol. Aging had a negative effect on intake of calories, fat, saturated fatty acids, and cholesterol. Cohort effects were not observed for any of these nutrients. Over time, intake of carbohydrates and cholesterol declined, while intake of polyunsaturated fatty acids rose.

Adult↗
PubMed1983

Prevention of the glucose intolerance of thiazide diuretics by maintenance of body potassium.

The effect of thiazide diuretics on the glucose tolerance of seven normal men in whom potassium loss was prevented with supplementation was studied using the glucose clamp technique. An initial control 2-h hyperglycemic clamp was performed to create a square wave of hyperglycemia 125 mg/dl above basal. At 1 h, 40 g glucose/m2 body surface area was ingested. Serial insulin (IRI) and gastric inhibitory polypeptide (GIP) levels were measured as well as the level of glucose infusion necessary to maintain the stable hyperglycemic level. After the initial study, subjects were placed on a 10-day course of 100 mg hydrochlorothiazide and 80 meq potassium per day. Subjects were monitored for dietary potassium intake, urinary potassium, and sodium losses, and the replacement of potassium adjusted accordingly. A repeat glucose clamp was done on day 10. When potassium losses were prevented, thiazides induced no alterations in glucose tolerance, beta-cell sensitivity to glucose, GIP-cell sensitivity to glucose, beta-cell sensitivity to GIP, or tissue sensitivity to insulin. Two control studies in which hypokalemia was allowed to ensue after hydrochlorothiazide ingestion revealed a diminution in glucose tolerance, a consequence of diminished pancreatic beta-cell response to glucose. We conclude that the thiazide effect on glucose tolerance is a consequence of the resultant hypokalemia that the diuretic may create.

Adolescent↗
PubMed1982

Feedback inhibition of insulin secretion by insulin: relation to the hyperinsulinemia of obesity.

We investigated the possible existence of a negative short-loop feedback of circulating insulin on the parent beta cell in 10 lean Caucasians, 10 obese Caucasians, and 10 obese Pima Indians. Plasma insulin levels were raised acutely by 100 microunits per milliliter for 90 minutes, and plasma glucose was maintained by the "clamp" technique. C-peptide levels were suppressed in all groups to approximately 50 per cent of basal values. However, the obese groups had absolute C-peptide levels much higher than those of the lean group. During the hour after infusion, the rate and magnitude of C-peptide recovery in the obese groups were higher than in the lean group. Thus, negative short-loop insulin-beta-cell feedback was operative in both the lean and obese states. Despite this suppression, the insulin-secretion rate in obese subjects was still greater than that in non-obese subjects. Inadequate feedback suppression may account in part for the prevailing hyperinsulinemia of the obese.

Adult↗
PubMed1982

Longitudinal changes in serum cholesterol in man: an epidemiologic search for an etiology.

Serum cholesterol levels were determined in 1011 male participants of the Baltimore Longitudinal Study of Aging. This study presents the longitudinal changes in serum cholesterol from 1 July 1963 to 30 June 1977. Serum cholesterol values dropped 6% between 1970 and 1972. The span of this study was divided into two eras, one preceding and one following the drop. The effects of obesity, selected dietary constituents and physical activity were examined in an attempt to explain the secular change in serum cholesterol. Serum cholesterol levels were not significantly correlated to levels of weight or body mass index. Changes in weight were significantly positively correlated with changes in serum cholesterol. Overall, however, the study population did not experience a significant drop in weight and therefore, this relationship could not explain the observed drop in serum cholesterol. There were virtually no significant correlations between the absolute value of any of the dietary variables examined and the absolute level of serum cholesterol. There were significant but small changes in most dietary constituents; however, only changes in caloric intake were significantly positively correlated with changes in serum cholesterol. Because the overall change in caloric intake was small, it could explain less than 1 mg/dl of the 11 mg/dl drop. There was no overall change in physical activity. No significant correlations were found between either the level or change in physical activity and the level or change in serum cholesterol. It is concluded that neither weight nor physical activity could account for the observed changes in serum cholesterol. Changes in dietary constituents were significant and in a direction which would predict a lower serum cholesterol. However, for the group, dietary changes could not fully explain the drop in serum cholesterol. For individuals, the changes in diet poorly predicted changes in serum cholesterol. It is suggested that the observed secular drop in serum cholesterol may be due to factor(s) other than those studied.

Adolescent↗
PubMed1982

Effect of age and obesity on fasting levels of glucose, insulin, glucagon, and growth hormone in man.

The influence of age and obesity on glucose homeostasis may be mediated via changes in basal levels of the main glucoregulatory hormones, insulin, glucagon, and growth hormone. Fasting plasma levels of these hormones and of glucose were measured in 186 normal male volunteers, 23 to 93 years old. Obesity was assessed as obesity index and by a more accurate anthropometric method as percentage of fat. Age and obesity index had a significant but low linear correlation (r = -.16, p less than .05). Age was not significantly correlated to any other metabolic variable. Percentage of fat was, however, significantly related to the fasting plasma levels of glucose (r = .27, p less than .001), insulin (r = .26, p less than .01), and glucagon (r = .16 less than .05). Fasting glucose was significantly correlated to insulin (r = .30 , p less than .001). These significant correlations persisted when age was held constant. In the basal state the main glucoregulatory hormones are not influenced by age, but plasma glucose, insulin, and glucagon levels are influenced by obesity.

Adult↗
PubMed1982

Effect of aging on the cardiothoracic ratio of men.

The potential usefulness of chest radiographs in the assessment of physical dimensions was examined in 243 men (age range 20-95 years) who had been followed up for an average of 12.3 years. From 1,124 of these films, measurements of cardiac diameter (CD) and thoracic diameter (TD) were made, and the cardiothoracic ratio (CTR) was calculated. Cross-sectional age differences were associated with a tendency toward increases in the CD and CTR throughout the lifespans of the 243 men, regardless of the presence or absence of heart disease. The thoracic diameter (TD) was greater in middle-aged than in young subjects, but less in the oldest than in the middle-aged subjects. Cumulative percentage curves for the CTR showed a shift to higher fiftieth to ninetieth percentile values with age. However, among the subjects free of heart disease, only one (age 95) had a CTR exceeding 50 per cent. Longitudinal analysis data agreed with the cross-sectional data. Forty-nine deceased subjects were matched with living subjects of the same heart disease classifications. Increases in the CD and CTR were predictive of death in the group with heart disease but not in the group without identifiable heart disease. An increase in CD was not correlated with an increase in systolic blood pressure. The decline in TD appeared to reflect a decline in rib-cage mobility with aging.

Adult↗