Effect of aging on pancreatic secretion in rats

Amylase and lipase levels in the metabolic syndrome and type 2 diabetes: A longitudinal study in rhesus monkeys

Latent associations between low serum amylase and reduced plasma insulin levels and increased adiposity have been described previously in a small study of asymptomatic middle-aged humans. In the present study, we sought to determine the nature of such changes during the longitudinal progression from metabolically normal to overt type 2 diabetes mellitus (T2DM) in nonhuman primates (NHPs), a disease that appears to be the same in both pathophysiology and underlying mechanisms as that which most commonly develops in middle-aged adult humans. Amylase and lipase levels were characterized in 157 unrelated adult rhesus monkeys (Macaca mulatta); 38% developed T2DM while under study. In all monkeys, multivariable linear regression analysis revealed that amylase could be negatively predicted by % body fat (β -0.29; p = 0.002), age (β -0.27; p = 0.005), and HbA1c (β -0.18; p = 0.037). Amylase levels were positively predicted by lipase levels (β = 0.19; p = -0.024) in all NHPs included in the study. Amylase was significantly lower in NHPs with metabolic syndrome (p < 0.001), prediabetes (PreDM) (p < 0.001), and T2DM (p < 0.001) compared to metabolically normal adult NHPs. Lipase increased in NHPs with PreDM (p = 0.005) and T2DM (p = 0.04) compared to normal NHPs. This is the first longitudinal study of any species, including humans, to show the dynamics of amylase and lipase during the metabolic progression from normal to metabolic syndrome, to PreDM and then to overt T2DM. The extraordinary similarity between humans and monkeys in T2DM, in pancreatic pathophysiology and in metabolic functions give these findings high translational value.

Structural characteristics of gut microbiota in longevity from Changshou town, Hubei, China

The gut microbiota (GM) and its potential functions play a crucial role in maintaining host health and longevity. The aim of this study was to investigate the potential relationship between GM and longevity. We collected fecal samples from 92 healthy volunteers (middle-aged and elderly: 43-79 years old; longevity: ≥ 90 years old) from Changshou Town, Zhongxiang City, Hubei, China. In addition, we collected samples from 30 healthy middle-aged and elderly controls (aged 51-70 years) from Wuhan, Hubei. The 16S rDNA V3 + V4 region of the fecal samples was sequenced using high-throughput sequencing technology. Diversity analysis results showed that the elderly group with longevity and the elderly group with low body mass index (BMI) exhibited higher α diversity. However, no significant difference was observed in β diversity. The results of the microbiome composition indicate that Firmicutes, Proteobacteria, and Bacteroidota are the core phyla in all groups. Compared to younger elderly individuals, Akkermansia and Lactobacillus are significantly enriched in the long-lived elderly group, while Megamonas is significantly reduced. In addition, a high abundance of Akkermansia is a significant characteristic of elderly populations with low BMI values. Furthermore, the functional prediction results showed that the elderly longevity group had higher abilities in short-chain fatty acid metabolism, amino acid metabolism, and xenobiotic biodegradation. Taken together, our study provides characteristic information on GM in the long-lived elderly population in Changshou Town. This study can serve as a valuable addition to the current research on age-related GM. KEY POINTS: • The gut microbiota of elderly individuals with longevity and low BMI exhibit higher alpha diversity • Gut microbiota diversity did not differ significantly between genders in the elderly population • Several potentially beneficial bacteria (e.g., Akkermansia and Lactobacillus) are enriched in long-lived individuals.

Understanding the gastrointestinal tract of the elderly to develop dietary solutions that prevent malnutrition

Although the prevalence of malnutrition in the old age is increasing worldwide a synthetic understanding of the impact of aging on the intake, digestion, and absorption of nutrients is still lacking. This review article aims at filling the gap in knowledge between the functional decline of the aging gastrointestinal tract (GIT) and the consequences of malnutrition on the health status of elderly. Changes in the aging GIT include the mechanical disintegration of food, gastrointestinal motor function, food transit, chemical food digestion, and functionality of the intestinal wall. These alterations progressively decrease the ability of the GIT to provide the aging organism with adequate levels of nutrients, what contributes to the development of malnutrition. Malnutrition, in turn, increases the risks for the development of a range of pathologies associated with most organ systems, in particular the nervous-, muscoskeletal-, cardiovascular-, immune-, and skin systems. In addition to psychological, economics, and societal factors, dietary solutions preventing malnutrition should thus propose dietary guidelines and food products that integrate knowledge on the functionality of the aging GIT and the nutritional status of the elderly. Achieving this goal will request the identification, validation, and correlative analysis of biomarkers of food intake, nutrient bioavailability, and malnutrition.

Age-associated changes in pancreatic exocrine secretion of the isolated perfused rat pancreas

Gut functions, such as gastrointestinal motility, gastric secretion and pancreatic secretion, were reduced with age. Glucose tolerance is impaired, and the release of insulin and β-cell's sensitivity on glucose are reduced with age. However, a lot of controversial data have been reported as insulin concentrations after glucose ingestion are either higher or no different in elderly and young subjects. Thus, this study was aimed to investigate whether aging could affect pancreatic exocrine secretion and its action mechanisms. An isolated perfused rat pancreatic model was used to exclude the effects of external nerves or hormones. Pancreatic secretion was increased by CCK under 5.6 mM glucose background in the isolated perfused pancreas of young (3 months), 12 months and 18 months aged rats. There was no significant difference between young and aged rats. In 3 months old rats, CCK-stimulated pancreatic secretion was potentiated under 18 mM glucose background. However, the potentiation effects of endogenous insulin and CCK were not observed in 12 and 18 months old rats. Exogenous insulin also potentiated CCK-stimulated pancreatic secretion in 3 months old rats. Similarly, exogenous insulin failed to potentiate CCK-stimulated pancreatic secretion as that of 3 months old rats. Wet weight of pancreas and amylase content in pancreatic tissue were not changed with age. These results indicate that pancreatic exocrine secretion is reduced with age and endogenous insulin secretion and/or action is involved in this phenomenon.

Age-dependent vulnerability to experimental acute pancreatitis is associated with increased systemic inflammation and thrombosis

The severity and mortality rates of acute pancreatitis (AP) are significantly elevated in the elderly population. However, due to a lack of appropriate animal models, the underlying mechanisms for this age-dependent vulnerability remain largely unknown. The purpose of this study was to characterize a murine model of AP, which displays age-associated severity, and to use this model to identify pathophysiologies that are distinctive of the aged with AP. AP was induced in young (4-5 months), middle-aged (12-13 months), and aged (23-25 months) C57BL/6 mice by repeated injection of caerulein, a homologue of the gastrointestinal hormone cholecystokinin. Approximately 10% of aged mice died during AP, while young and middle-aged mice showed no mortality. Although both young and aged mice exhibited early signs of edema and inflammation in the pancreas, kidney, and lung, young mice showed signs of recovery within 24 h, while aged mice exhibited increasingly severe tissue damage and cell death. There was a significant age-dependent increase in pancreatic neutrophil activation and systemic inflammation as assessed by pancreatic myeloperoxidase and plasma interleukin-6 (IL-6) concentration, respectively. Importantly, aged but not young mice with AP showed significantly elevated thrombosis in the lung and kidney as well as a marked increase in plasma concentration of plasminogen activator inhibitor-1 (PAI-1), a primary inhibitor of the fibrinolytic system. These results demonstrate that aging is associated with increased severity of AP characterized by augmented and prolonged pancreatic inflammation and the presence of multiple extra-pancreatic sequelae including thrombosis.

Age-dependent reduction of the PI3K regulatory subunit p85α suppresses pancreatic acinar cell proliferation

The phosphatidylinositol 3-kinase (PI3K)/Akt pathway is important for tissue proliferation. Previously, we found that tissue regeneration after partial pancreatic resection was markedly attenuated in aged mice as compared to young mice and that this attenuation was because of an age-dependent reduction of PI3K/Akt signaling in the pancreatic acini; however, the mechanisms for the age-associated decline of pancreatic PI3K/Akt signaling remained unknown. To better delineate the mechanisms for the decreased PI3K/Akt activation with aging, age-associated changes in cell proliferation and PI3K/Akt signaling were investigated in the present study using in vitro primary pancreatic acinar cell cultures derived from young and aged mice. In response to treatment with insulin-like growth factor 1 (IGF-1), acinar cells from young but not aged mice showed increased activation of PI3K/Akt signaling and cell proliferation, indicating that intrinsic cellular mechanisms cause the age-associated changes in pancreatic acinar cells. We also found that the expression of PI3K p85α subunit, but not IGF-1 receptor or other PI3K subunits, was significantly reduced in pancreatic acinar cells from aged mice; this age-associated reduction of p85α was confirmed in both mouse and human pancreatic tissues. Finally, small interfering RNA (siRNA)-mediated knockdown of p85α expression in acinar cells from young mice resulted in markedly attenuated activation of PI3K/Akt downstream signaling in response to IGF-1. From these results, we conclude that exocrine pancreatic expression of PI3K p85α subunit is attenuated by aging, which is likely responsible for the age-associated decrease in activation of pancreatic PI3K signaling and acinar cell proliferation in response to growth-promoting stimuli.

Age-related alterations in Ca2+ signals and mitochondrial membrane potential in exocrine cells are prevented by melatonin

Information regarding age-induced Ca(2+) signal alterations in nonexcitable cells is limited. In addition, little evidence exists on the ability of melatonin to palliate the effects of aging on Ca(2+) signals and mitochondrial potential, a parameter involved in both Ca(2+) signaling and aging. We studied the ability of melatonin to prevent the effects of aging on intracellular Ca(2+) homeostasis and mitochondrial potential in exocrine cells. Pancreatic acinar cells were obtained from adult (3 months old) and aged (22-24 months old) mice by collagenase dispersion. Ca(2+) signals, in situ mitochondrial potential and in vitro amylase secretion were determined. Secretion in response to increasing levels of the secretagogues, acetylcholine and cholecystokinin (CCK), were impaired in aged pancreatic acini. This decrease was accompanied by an inhibition in the amplitude of the peak response to maximal concentrations of the agonists, and by a decrease in the pattern of Ca(2+) oscillations induced by postprandial levels of CCK. Both the size of the calcium pools, assessed by low levels of ionomycin, and capacitative calcium entry, induced by depletion of the stores with thapsigargin, were diminished in aged cells. These changes in Ca(2+) homeostasis were associated with depolarization of intracellular mitochondria. Oral administration of melatonin for 3 months to aged mice restored the secretory response, the amplitude and frequency of Ca(2+) responses, the size of intracellular calcium pools, the capacitative calcium entry, and the mitochondrial potential. In conclusion, melatonin restores secretory function, Ca(2+) signals and mitochondrial potential of aged exocrine cells.

Aging is associated with decreased pancreatic acinar cell regeneration and phosphatidylinositol 3-kinase/Akt activation

BACKGROUND & AIMS

The effects of aging on pancreatic acinar cell proliferation have not been clearly defined. Phosphatidylinositol 3-kinase (PI3K)-mediated phosphorylation of Akt is a critical step for proliferation of various cell types and insulin secretion from pancreatic endocrine cells; however, its role in acinar cell proliferation is not known. The purpose of this study was to (1) delineate the effects of aging on pancreatic regeneration after partial pancreatectomy (Px) and (2) define the involvement of the PI3K/Akt pathway in pancreatic regeneration.

METHODS

Following partial Px, pancreatic regeneration and activation of the PI3K pathway were compared in young and aged mice. Activation of the PI3K/Akt pathway was evaluated by Akt phosphorylation (pAkt). The role of the PI3K pathway in pancreatic regeneration after partial Px was assessed by effects of a pharmacologic PI3K inhibitor wortmannin or small interfering RNA (siRNA) to the p85alpha regulatory subunit. To confirm further the critical role of the PI3K/Akt pathway in pancreatic acinar cell proliferation, IGF-1-mediated cell proliferation was determined in cultured acinar cells pretreated with wortmannin or p85alpha siRNA.

RESULTS

Pancreatic regeneration and pAkt expression after partial Px were significantly decreased with aging. Treatment with wortmannin or p85alpha siRNA reduced pancreatic regeneration after partial Px. The IGF-1-mediated cell proliferation in vitro was completely blocked by wortmannin or p85alpha siRNA but not by the MEK/ERK inhibitor PD98059.

CONCLUSIONS

PI3K/Akt activation plays a critical role in the regeneration of pancreatic acini after resection. Furthermore, pancreatic regeneration is markedly attenuated in the aged pancreas most likely because of decreased PI3K/Akt activation.

Manifestations of experimental acute pancreatitis in young and old rats

Two kinds of experimental pancreatitis were induced in young (4-6 month) and old (25-27 month) female Wistar rats: acute edematous pancreatitis was induced by intraperitoneal administration of a high dose of cerulein (40 micro/kg x 2) and acute hemorrhagic pancreatitis was intraductal injection of 1% deoxycholic acid. After these treatments, the plasma amylase concentration and pancreatic wet weight were determined and the pancreas was examined histologically. In the groups with cerulein induced pancreatitis one of eight old rats died, whereas all five young rats survived. There was no specific finding macroscopically in the liver, kidney, lung or heart of old rats at autopsy after cerulein injection. The plasma amylase concentration and the pancreatic wet weight were significantly increased by administration of cerulein or deoxycholic acid in both young and old rats. There was no significant difference in the plasma amylase concentrations in young and old rats after the induction of acute pancreatitis. The increase in pancreatic wet weight was less in old rats than in young ones after deoxycholic acid treatment, but similar in the two groups after cerulein injection. The extents of histological changes were also similar in young and old rats. Thus, no evidence that aging increases susceptibility to pancreatitis was obtained.

Diarrhea and malabsorption in the elderly

Physicians who care for elderly patients should be alert to the possible presence of diarrhea and malabsorption. Older patients may not admit to having chronic diarrhea, particularly if they also are incontinent. If diarrhea is of short duration, an infectious cause is at least as common as in the young. Institutionalized elderly are particularly prone to gastrointestinal infections, but the manifestations may not be overt. When an intestinal infection and potential medication-induced gastrointestinal disturbances have been excluded, the differential diagnosis of diarrhea in the elderly is the same as in the young. Causes include intestinal malabsorption, even though diarrhea is a less common manifestation of malabsorption in the old than in younger patients. In the elderly, micronutrient deficiency is a common presenting clinical picture; because the symptoms of malabsorption are covert, the diagnosis often is delayed, and nutritional deficiencies are more common and more severe than in the young. Because the elderly have less nutritional reserve than the young, these deficiencies are clinically much more devastating in the elderly. Although the causes of malabsorption, as a whole, are similar in older and younger patients, chronic pancreatic insufficiency of unknown cause and intestinal bacterial overgrowth without an anatomic abnormality of the small intestine are syndromes that are specific to the elderly and must be considered in any older patient with unexplained weight loss or failure to thrive. Often, therapeutic trials are necessary to establish a potential diagnosis.

A pancreatic extract-enriched diet improves the nutritional status of aged rats

Correction of the malnourished state, particularly common and severe in elderly people, is often unsuccessful. To improve the efficiency of realimentation, we evaluated the nutritional effect of a pancreatic extract (PE)-enriched diet in malnourished aged rats. Sprague-Dawley male rats were randomly assigned to 6 groups as follows: 1 group of control rats had free access to the diet for 12 wk (C group) and 5 groups were 50% food restricted for the same period. One food-restricted group was then killed (R group) and the 4 remaining groups were refed for 1 wk using a standard diet enriched either with two different doses of a pancreatic extract (2.4 or 4.8 g/d in PE1 and PE2 groups, respectively) or with an isonitrogenous casein hydrolysate (CH1 and CH2 groups, respectively). Profound alterations induced by food restriction (FR) were moderately corrected by refeeding, except nitrogen balance, which was reestablished in rats refed all diets (P: < 0.01 vs. R). Supplementation of the food ration with a pancreatic extract clearly improved recovery. Indeed, body weight gain, both jejunal and ileal trophicity [jejunum: total height, PE2: 849 +/- 45 microm vs. CH2: 768 +/- 17 microm (P: < 0.05); protein content, PE2: 69.9 +/- 5.7 mg vs. CH2: 56.4 +/- 4.8 mg (P: < 0.01)] and nonspecific immune response in terms of H2O2 production by polymorphonuclear neutrophils and tumor necrosis factor alpha (TNF-alpha) by macrophages (PE2, 20.7 +/- 4.7 vs. CH2, 8.7 +/- 2.3, P: < 0.05) were improved in rats fed PE2. A pancreatic extract could improve the efficiency of realimentation in malnourished aged rats.

Changing perspectives on aging and energy requirements: aging and digestive function in humans, dogs and cats

When considering the question of energy balance, it is important to take into account energy provision and the ability of aging animals to digest macronutrients and thus obtain their maintenance energy requirement. A large number of studies have been conducted in humans in an effort to establish whether aging of the gastrointestinal tract has a significant effect on availability of dietary energy. The results of these studies have been conflicting, with indications that some aspects of gut functionality do decline with age, but little evidence overall to suggest that aging humans are at risk of energy deficit due to compromised digestive efficiency. A number of digestibility studies carried out with dogs confirm that there is no evidence of an age-related decline in digestive efficiency. This knowledge makes the determination of energy provision to senior dogs relatively straightforward to calculate. Many senior cats appear to exhibit quite a marked reduction in their ability to digest macronutrients, particularly fat, efficiently. Because this reduces the overall capacity to obtain energy from the diet, it is recommended that old cats should not routinely be offered reduced energy diets. For senior cats, the feeding regimen in later life should be to offer highly digestible diets that provide as much energy as adult maintenance rations.

Effect of ageing on pancreatic hyperplasia after 90% proximal small bowel resection

The present study was performed to examine the effect of ageing on pancreatic hyperplasia observed after proximal small bowel resection (PSBR). Young and old Wistar rats were randomly assigned to two groups, which underwent either an approximate 90% PSBR or a jejunal and ileal transection (TRC). One week after the operation, the pancreatic wet weight and the protein, DNA and RNA content of the pancreas were all significantly higher in young PSBR rats than in young TRC rats. However, no differences were seen in the old rat groups. Plasma enteroglucagon levels were elevated in both young and old PSBR rats, but the ratio of increase between the PSBR and TRC groups was significantly higher in young rats. Plasma cholecystokinin and gastrin levels did not increase after PSBR in either the young or old rats. These findings suggest that pancreatic hyperplasia observed after PSBR is attenuated by ageing, probably due to an insufficient increase in plasma enteroglucagon levels.

Effects of pancreatic duct ligation and aging on acute taurocholate-induced pancreatitis. Experiments in the perfused pancreas in rats

CONCLUSION

When taurocholate was injected into the common bile duct, high ductal pressure due to ligation of the pancreatic duct did not produce more damage in the pancreas of both old rats and young adult rats, and levels of pancreatic enzymes in portal venous effluent were lower in old rats than in younger rats.

BACKGROUND

The effects of ligation of the pancreatic duct and aging on acute pancreatitis caused by taurocholate are still unclear.

METHODS

Young adult and old male Wistar rats were used. Six hours after ligation of the common bile duct in both the duodenum and liver hilus, rats were killed and the pancreata were perfused. Taurocholate or normal saline was injected retrogradely into the common bile duct. The levels of amylase and lipase in the portal venous effluent were determined as markers of damage to the pancreas. The pancreas was also histologically examined after the perfusion experiments using an Image Analysis System.

RESULTS

(1) A nonsignificant elevation of pancreatic enzymes was found in portal venous effluent by the retrograde injection of saline into the common bile duct. Injection of taurocholate caused a marked elevation of enzymes in the effluent for the first 30 min after injection, which then gradually decreased. (2) Basal levels of pancreatic enzymes were significantly higher in the ligation group than in the nonligation group. Injection of saline into the common bile duct had no apparent effect on enzymes in the effluent. In contrast, taurocholate injection into the common bile duct produced a marked increase in enzymes in the portal venous effluent. However, no significant difference was found between the ligation group and the nonligation group. (3) Similar findings were obtained when old rats were used. (4) Although basal levels of enzymes were almost the same in nonligated old and young adults rats, taurocholate injection into the pancreatic duct in old rats resulted in a significant depression of enzymes compared to that in young adult rats. In the ligation group, pancreatic enzymes in the portal venous effluent following taurocholate injection tended to be lower in old rats than in young adult rats. The results were histologically supported in that various degrees of fibrosis were found in the pancreata of old rats.

Supplementation of oral nutrition with pancreatic enzymes improves the nutritional status of aged endotoxemic rats

Malnutrition is a common problem in elderly people. The association of malnutrition and physical illness or injury leads to both localized and general complications. In particular, impairment of the adaptive response of pancreatic function to undernutrition and refeeding may adversely affect nutritional status and elicit morbidity and mortality. Aged rats (24 mo old) were treated with lipopolysaccharide (LPS) from E. Coli (3 mg/kg body weight). Six days later, survivors were randomized to receive, for 7 days, an oral chow diet enriched with either a pancreatic extract (PE) (2.4 mg/day) or an isonitrogenous supply of casein (CAS). Endotoxemia induced a catabolic state, with a body weight loss of 7.6 +/- 1.1% on day two after LPS treatment. Mean food intake from day 6 to day 13 was similar in LPS-PE and LPS-CAS groups (19.0 +/- 5.6 versus 19.7 +/- 6.9 g). The metabolic response varied according to the type of muscle studied. In fast (white) muscle, the protein content and the glutamine pool remained markedly depleted in endotoxemic rats receiving casein supplementation. In contrast, enrichment of nutrition with PE significantly limited the LPS-induced muscle wasting and increased the muscle glutamine content. As in previous observations, no significant change occurred in slow (red) muscle. These results could indicate that PE supplementation counteracts pancreatic deficiency caused by aging and worsened by stress and this, in turn, could improve the efficiency of nutrition, to support the hypermetabolism of aged injured rats.

Sex difference in gene expressions of cholecystokinin (CCK) and CCK receptor in young and old rats

The gene expressions of cholecystokinin (CCK) in the proximal small intestinal mucosa and CCK-A receptor in the pancreas were examined in male and female young (4-8 months old) and old (26-29 months old) rats. Their concentrations of CCK in the intestine were also compared. In males, but not in females, the mRNA levels of CCK in the intestine and those of the CCK-A receptor in the pancreas were significantly lower in old than young rats. In females, but not in males, the tissue content of CCK in the proximal intestinal mucosa was significantly higher in old rats. The pancreatic wet weight and trypsin activity in the proximal lumen were similar in young and old rats of both sexes. Therefore, changes in the regulations of gene expressions of CCK and the CCK receptor with age differ in male and female rats.

Evidence for the effect of aging on tissue contents of gastrin, cholecystokinin and somatostatin in the rat

The changes associated with aging in the tissue concentrations of cholecystokinin, somatostatin and gastrin in young (7-month-old), middle-aged (13-month-old) and old (25-26-month-old) rats were investigated. The concentrations and total contents of somatostatin and gastrin significantly decreased in the antrum in 13- and 25-26-month-old rats compared with the young controls. The cholecystokinin concentration in the proximal intestine and its total content significantly increased in the old rats. Somatostatin concentrations in the intestine and cerebral cortex did not change with age. Cholecystokinin content in the cerebral cortex decreased in old rats because of the decrease of tissue wet weight. We conclude that the effects of aging on the changes of peptide concentrations in tissues vary depending on peptide specie and in different tissues studied.

Age-related differences of cholecystokinin receptor binding in the rat brain

1. Cholecystokinin and benzodiazepine receptor binding was evaluated in 2-, 9- and 18-month old rats in the brain regions where cholecystokinin octapeptide and gamma-aminobutyric acid are known to coexist in common nerve cells (frontal cortex, hippocampus). 2. There was a regionally selective alteration of hippocampal 3H-CCK-8 binding in the oldest age group, if compared to both young and adult animals. Non-linear regression analysis of binding data revealed significantly lower apparent number of binding sites (Bmax), and twofold (but not statistically significantly) higher binding affinity for the radiolabelled ligand. No differences between any age groups in 3H-flunitrazepam binding to benzodiazepine receptors were found. 3. The results suggest that changes in cholecystokinin receptor characteristics might contribute to the behavioural impairments in aged rats.

Gastrin affects enzyme activity and gene expression in the aging rat pancreas

The structural and functional properties of the pancreas are known to be affected by a number of hormones, particularly those of the gastrin-CCK family, yet little is known about the responsiveness of the pancreas to gastrin-CCK peptides during the latter stages of life. The present investigation examined the changes in pancreatic growth, the activity, and the steady-state mRNA levels of some of the digestive enzymes during advancing age and after administration of gastrin. Groups of 3-, 6-, 12-, and 16-month-old male Fischer-344 rats were infused (osmotic minipump) with either gastrin G-17 (250 ng/kg/h) or saline (controls) for 14 days. In control pancreas, aging resulted in slight progressive reduction in pancreatic DNA, RNA, and protein concentrations. This decrease was markedly enhanced by gastrin treatment in 16-month-old rats. Pancreatic amylase and trypsin (TRP) activities in these animals were also slightly decreased with aging, whereas the steady-state mRNA levels of both enzymes were significantly higher in 16-month-old rats than in their 3-month-old counterparts. However, in 16-month-old rats, the steady-state mRNA levels of amylase and TRP were significantly reduced after gastrin administration, when compared with the corresponding controls. Chymotrypsin (CHY) activity in the pancreas remained essentially unchanged between 3- and 12-month-old rats, but in 16-month-old animals it was markedly decreased. CHY activity was further reduced by gastrin treatment only in the 16-month-old group.(ABSTRACT TRUNCATED AT 250 WORDS)

Bladder dysfunction in the elderly

Bladder dysfunction in the elderly is an enormous public health problem. Laboratory research using animal models has to date not yielded clinically useful new information. Demographic and urodynamic studies in selected elderly patients indicate that neurological disease and bladder outlet obstruction are the primary causes for voiding dysfunction. The effect of aging per se on the urinary bladder is not known. Elderly patients who have bladder dysfunction should be evaluated with a careful history and physical examination combined with a practical urodynamic evaluation rather than simply being labeled as having "bladder dysfunction in the elderly."

Aging and pancreatic exocrine function. Studies in female conscious rats

Basal pancreatic exocrine functions as well as responses to endogenous (BPJ diversion) and exogenous (injection of CCK-8 or secretin) stimulations were examined in young (6- and 12-month-old) and old (24- to 26-month old) female Fischer 344 rats. Basal secretions were not significantly different between young and old rats. BPJ diversion significantly stimulated pancreatic secretions of fluid, bicarbonate, and protein in all animals. The pancreatic protein response (mg/kg/hr) to BPJ diversion was significantly attenuated with respect to age [57.59 +/- 16.16, 43.73 +/- 6.94, and 20.75 +/- 3.95, for 6-, 12-, 24- to 26-month-old rats, respectively, mean +/- SE, F(2,20) = 3.49, P less than 0.05]. The pancreatic responses to secretin (0.086, 0.432, and 1.728 nmol/kg) were not significantly different between young and old rats. Intravenous injection of CCK-8 (0.033, 0.167, and 0.667 nmol/kg) produced a significant increase in protein output in all age groups. In young animals, stepwise increases in protein output were observed, whereas, in old rats, increments in response to the larger two doses of CCK-8 (0.167 and 0.667 nmol) were smaller than that produced by 0.033 nmol/kg of CCK-8. In conclusion, the basal secretions in old rats were comparable with those in young ones, but the reserve capacity for protein secretion appears to decrease in old compared to young rats.

Effects of age on urinary bladder function in the male rat

In a previous study we investigated the effects of age on the micturition characteristics and bladder function of male Fischer rats ages five to seven, 16 to 18 and 22 to 24 months. The 24 hr. water intake and urine output increases significantly with age; 22 to 24 month rats showed a 39% increase in water intake and a 93% increase in urine output compared to five to seven month rats. The intravesical pressure at micturition is 100% greater in 22 to 24 month and 16 to 18 month rats compared to five to seven month old rats with no age-related change in bladder volume at micturition. In the present study, in vitro bladder capacity did not differ between the three age groups although the average plateau pressure significantly decreased with advancing age. Using the isolated whole bladder model, the contractile response to the autonomic agonists bethanechol, phenylephrine, and isoproterenol did not change significantly with age. Similarly, there were no age-related changes in the response of the bladder to non-autonomic drugs (histamine, oxytocin, serotonin, substance P, and PGF2 alpha) except for PGF2 alpha which produced an age-related increase in the maximum bladder contraction. In summary, while in vivo micturition clearly changes with age, the in vitro contractility of the bladders to autonomic agents did not. Therefore, age related differences in micturition would be related primarily to the changes in neuronal innervation and central control of micturition rather than alterations in the contractility of the bladder. In addition, these studies show the importance of correlating in vivo bladder function (micturition frequency and volume, cystometry and urodynamics) with in vitro contractile and functional studies.

Exocrine pancreatic secretion in the elderly

In order to evaluate impairment of exocrine pancreatic function during aging, 27 subjects (mean age: 36 years +/- 7.8) and 28 subjects (mean age: 72 years +/- 3.2), with no clinical or radiological evidence of digestive disease, were selected. Duodenal aspirates over a 60 min period were obtained during continuous IV infusion of secretin (0.5 U/kg/h) and caerulein (75 ng/kg/h). Bicarbonate, lipase, chymotrypsin amylase concentrations and output were measured. Bicarbonate, lipase, chymotrypsin concentrations in the aged group were significantly reduced by 17%, 15% and 23% respectively (P less than 0.05) as compared with those in the young group. In addition, a significant reduction of approximately 45% in bicarbonate and enzyme output levels was observed. This study provides strong evidence for a marked functional involution of the exocrine pancreatic secretion during aging. The potential consequences of this phenomenon on the nutritional status in the elderly are discussed.

Development and age-related changes in pancreatic cholecystokinin receptors and duodenal cholecystokinin in guinea pigs

We have investigated the changes associated with development and aging on the interrelationships between cholecystokinin (CCK) and the pancreas in the guinea pig. Three groups (1 month old, 1 year old, and 3 years old) of male guinea pigs were sacrificed while feeding in order to measure food-stimulated levels of CCK in blood and in duodenal mucosa by radioimmunoassay (RIA), as well as the pancreatic concentrations of CCK receptors. Systemic blood concentrations of CCK did not change with age. However, the concentration and content of CCK in duodenal mucosa increased more than 3-fold with age. A single class of high-affinity (KD less than or equal to 0.1 nM) CCK-receptor was found on the pancreatic membranes. The concentration (fmol/mg protein) of these receptors significantly diminished by one-half with increasing age. We also found an apparently similar fall in the receptor-binding affinity, but the difference was not significant. We conclude that in the guinea pig, duodenal content of CCK increases so as to compensate for the decreasing concentration of pancreatic CCK receptors, or, perhaps, vice versa. The diminished exocrine function of the pancreas, seen with increasing age, may well reflect both the diminished number of CCK-receptors and the reduction of pancreatic acinar cells.

Effect of age on in vivo urinary bladder function in the rat

The effects of age on micturition in male Fischer 344 rats, ages five to seven, 16 to 18 and 22 to 24 months, were studied. The 24 hr. water intake, 24 hr. urine output, frequency and volume of each micturition were obtained from rats housed individually in metabolic cages. Intravesical pressure and volume at which the micturition contraction occurred were evaluated using natural-fill cystometry. The 24 hr. water intake and urine output increased significantly with advancing age; 22 to 24 months rats showed a 39% increase in water intake and a 93% increase in urine output compared to five to seven month rats. The increase in urine output observed in the 22 to 24 month old rats was manifested by a 95% increase in volume per micturition and a 52% increase in frequency of micturition compared to five to seven month old rats. The pressure at micturition (PAM) was 100% greater in 22 to 24 and 16 to 18 month old rats compared to five to seven month old rats with no age-related difference in bladder volume at micturition (BVM). These studies demonstrate that in vivo micturition changes with age in the male F344 rat. Although there were no overt urological dysfunctions observed in the aging rats, the alterations in function would indicate that there were changes in either the mechanisms controlling micturition, or changes in the musculature itself. These possibilities will be the subject of further investigations.

Influence of aging upon pancreatic digestive enzymes

The effects of aging upon pancreatic digestive enzymes were studied in 27- and 3-month-old Fischer 344 rats. Mean pancreatic weight, protein and DNA concentration and content, and protein-DNA ratios did not differ in the two groups of animals. Pancreatic amylase concentration was reduced by 41% and lipase concentration was increased by 29% in the aging animals, whereas, trypsinogen concentrations did not differ. Young and aging rats were fed diets enriched with fat (72%) or sucrose (75%) for seven days to define whether the different enzyme contents were intrinsic to the aging process or adaptable. In young, but not in aging rats, lipase concentration increased 25% during high fat compared to high sucrose diet feeding. High starch diet feeding induced a 26% increase in amylase in young rats but not in the old. Trypsinogen concentration was unaffected by dietary manipulation. Jejunal enteropeptidase concentration was modestly reduced in the aging rat. Postprandial luminal concentrations of trypsin and amylase did not differ in the two groups. Thus, aging may induce modest changes in pancreatic digestive enzymes and in jejunal enteropeptidase which are unlikely to be physiologically important. However, the pancreas of aging rats does not adapt to changes in dietary intake as well as young rats.