Insulin resistance is accompanied by impairment of amylase-gene expression in the exocrine pancreas of the obese Zucker rat

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.

Female and male obese Zucker rats display differential inflammatory mediator and long non-coding RNA profiles

AIMS

The goal of this study was to identify mediators in peri-lymphatic adipose tissue (PLAT) that are altered in obese versus lean Zucker rats, with focus on potential sex differences MAIN METHODS: Mesenteric PLAT was analyzed with protein and lncRNA arrays. Additional RT-PCR confirmation was performed with epididymal/ovarian fat.

KEY FINDINGS

MCP-1, TCK-1, Galectin-1, Galectin-3, and neuropilin-1 were elevated in PLAT from obese rats of both sexes. However, 11 additional proteins were elevated only in obese males while 24 different proteins were elevated in obese females. Profiling of lncRNAs revealed lean males have elevated levels of NEAT1, MALAT1 and GAS5 compared to lean females. NEAT1, MALAT1, and GAS5 were significantly reduced with obesity in males but not in females. Another lncRNA, HOTAIR, was higher in lean females compared to males, and its levels in females were reduced with obesity. Obese rats of both sexes had similar histologic findings of mesenteric macrophage crown-like structures and hepatocyte fat accumulation.

SIGNIFICANCE

While obese male and female Zucker rats both have increased inflammation, they have distinct signals. Future studies of the proteome and lncRNA landscape of obese males vs. females in various animal models and in human subjects are warranted to better guide development of therapeutics for obesity-induced inflammation.

Glucose homeostasis dependency on acini-islet-acinar (AIA) axis communication: a new possible pathophysiological hypothesis regarding diabetes mellitus

Studies have highlighted the existence of two intra-pancreatic axes of communication: one involved in the regulation of enzyme production by insulin-the insular-acinar axis; and another involved in the regulation of insulin release by pancreatic enzymes-the acini-insular axis. Previous studies by our laboratory show that pancreatic enzymes can affect blood glucose homeostasis and insulin secretion independently of their digestive functions, both from the gut lumen and probably from the blood. As a result we would like to introduce here the concept of acini-islet-acinar (AIA) axis communication (feedback), which could play an important role in the development of obesity and diabetes type 2. The AIA feedback links the endocrine and exocrine parts of the pancreas and emphasizes the essential role that the pancreas plays, as a single organ, in the regulation of glucose homeostasis by amylase most probably in gut epithelium and by insulin and glucagon in peripheral blood.

Experiments suggesting extra-digestive effects of enteral pancreatic amylase and its peptides on glucose homeostasis in a pig model

The studies presented were designed to highlight the impact of pancreatic enzymes on glycemic control and insulin response. Blood glucose and plasma insulin levels were monitored after intravenous, oral or direct gut glucose tolerance tests (GTT) in 6 pigs with an intact gastrointestinal tract and in 12 pigs following duodenal-jejunal bypass (DJB) surgery. In the intact pigs, pancreatic enzymes (Creon®) given orally 1 h prior to the GTT, lowered the blood glucose levels during the oral and meal GTT and reduced the plasma insulin response during the intravenous and meal GTT. In DJB pigs, blood glucose and plasma insulin levels were higher following glucose loading into the by-passed biliopancreatic limb as compared to that following glucose loading orally or into the common intestinal limb. Infusion of amylase or amylase peptides together with glucose into the biliopancreatic limb lowered blood glucose levels in DJB pigs. These preliminary data suggest new, extra-digestive, actions of enteral pancreatic enzymes – probably amylase or its peptides – on glucose homeostasis, with an reduction in net glucose absorption into the blood and in insulin response. This ability of digestive enzymes (amylase) to reduce post-prandial hyperglycaemia in an insulin-independent manner could aid in preventing the development of obesity and diabetes.

Association between non-alcoholic fatty pancreatic disease (NAFPD) and the metabolic syndrome: case-control retrospective study

Background

Fatty liver is associated with insulin resistance, dyslipidemia, and obesity and is therefore considered a phenotype of metabolic syndrome. However, less is known regarding the metabolic abnormalities associated with non-alcoholic fatty pancreatic disease (NAFPD; fatty pancreas). The present study was performed to ascertain whether fatty pancreas is associated with specific metabolic risk factors and with metabolic syndrome as defined by the Adult Treatment Panel III.

Methods

Five-hundred-fifty-seven healthy and consecutive subjects without known hypertension or diabetes and who received a health investigation at the National Taiwan University Hospital Health Management Center were enrolled in this retrospective study. Fatty pancreas was diagnosed via trans-abdominal ultrasonographic findings.

Results

Seventy-two (12.9%) subjects diagnosed with fatty pancreas comprised the fatty pancreas group, and remaining subjects comprised the normal pancreas group. The presence of various demographic and metabolic risk factors was recorded for all subjects, and the two groups were examined for statistically significant differences in these factors. As compared to the absence of fatty pancreas, the presence of the disease was associated with older age and with higher values for each of the following: BMI, abdominal girth/height, abdominal girth (both genders), fasting and postprandial blood glucose, HbA1c, total cholesterol, triglycerides, LDL-cholesterol, systolic blood pressure, and platelet count. In contrast to previously reported findings, serum amylase values were lower in the fatty pancreas as compared to the control group.

Conclusion

The presence of fatty pancreas represents a meaningful manifestation of metabolic syndrome together with obesity.

Revisiting the cardiometabolic relevance of serum amylase

Background

The pancreas has dual functions as a digestive organ and as an endocrine organ, by secreting digestive enzymes and endocrine hormones. Some early studies have revealed that serum amylase levels are lower in individuals with chronic pancreatitis, severe long-term type 2 diabetes or type 1 diabetes. Regarding this issue, we recently reported that low serum amylase levels were associated with metabolic syndrome and diabetes in asymptomatic adults. In the light of this, we further investigated the fundamental relationship between serum amylase and cardiometabolic aspects by reanalyzing previous data which comprised subjects without diabetes treatment with oral hypoglycemic drugs or insulin (n = 2,344).

Findings

Serum amylase was inversely correlated with body mass index independently of age. Higher serum amylase levels were noted in older subjects aged 55 years old or more (n = 1,114) than in younger subjects (P < 0.0001, ANOVA), probably due to lower kidney function. It was likely that serum amylase may act similarly to other cardiometabolic protective factors such as high-density lipoprotein cholesterol. However, serum amylase levels were significantly lower in drinkers, particularly daily drinkers (n = 746, P < 0.0001, ANOVA). Meanwhile, despite of consistent inverse relationship between serum amylase and fasting plasma glucose, the relationship between serum amylase and HbA1c may be rather complicated in individuals with normal or mildly impaired glucose metabolism (up to HbA1c 6.0% (NGSP)).

Conclusions

Revisiting the cardiometabolic relevance of serum amylase may yield novel insight not only into glucose homeostasis and metabolic abnormalities related to obesity, but also possibly carbohydrate absorption in the gut.

Low serum amylase in association with metabolic syndrome and diabetes: A community-based study

Background

Low serum amylase levels may reflect impaired exocrine-endocrine relationship in the pancreas. However, few clinical studies have addressed this issue. Therefore, in this epidemiological study, we investigated whether low serum amylase was associated with the pathogenesis of impaired insulin action: metabolic syndrome (MetS) and diabetes.

Research Design and Methods

Serum amylase, cardiometabolic risk factors, MetS (Adult Treatment Panel III criteria), and diabetes were examined in 2,425 asymptomatic subjects aged 30-80 years who underwent medical checkups recently (April 2009-March 2010) and 5 years ago.

Results

Clinical variables, except for age and estimated glomerular filtration rate (eGFR), shifted favorably with increasing serum amylase levels. Plasma glucose levels at 1- and 2-hr during OGTT increased significantly with decreasing serum amylase levels. Multiple logistic analyses showed that, compared with highest quartile of serum amylase, lowest quartile was associated with increased risk for MetS and diabetes after adjustment for confounding factors [odds ratio (95% CI), 2.07 (1.39-3.07) and 2.76 (1.49-5.11), respectively]. In subjects who underwent checkups 5 years ago (n = 571), lower amylase at the previous checkup were associated with larger numbers of metabolic abnormalities at the recent checkup. The fluctuation over time in serum amylase levels in subjects with low serum amylase at the previous checkup was slight and was unaffected by kidney dysfunction.

Conclusions

Our results indicate that low serum amylase is associated with increased risk of metabolic abnormalities, MetS and diabetes. These results suggest a pancreatic exocrine-endocrine relationship in certain clinical conditions.

Experimental evidence of obesity as a risk factor for severe acute pancreatitis

The incidence of acute pancreatitis, an inflammation of the pancreas, is increasing worldwide. Pancreatic injury is mild in 80%-90% of patients who recover without complications. The remaining patients may develop a severe disease with local complications such as acinar cell necrosis, abscess and remote organ injury including lung injury. The early prediction of the severity of the disease is an important goal for physicians in management of patients with acute pancreatitis in order to optimize the therapy and to prevent organ dysfunction and local complications. For that purpose, multiple clinical scale scores have been applied to patients with acute pancreatitis. Recently, a new problem has emerged: the increased severity of the disease in obese patients. However, the mechanisms by which obesity increases the severity of acute pancreatitis are unclear. Several hypotheses have been suggested: (1) obese patients have an increased inflammation within the pancreas; (2) obese patients have an increased accumulation of fat within and around the pancreas where necrosis is often located; (3) increase in both peri- and intra-pancreatic fat and inflammatory cells explain the high incidence of pancreatic inflammation and necrosis in obese patients; (4) hepatic dysfunction associated with obesity might enhance the systemic inflammatory response by altering the detoxification of inflammatory mediators; and (5) ventilation/perfusion mismatch leading to hypoxia associated with a low pancreatic flow might reduce the pancreatic oxygenation and further enhance pancreatic injury. Recent experimental investigations also show an increased mortality and morbidity in obese rodents with acute pancreatitis and the implication of the adipokines leptin and adiponectin. Such models are important to investigate whether the inflammatory response of the disease is enhanced by obesity. It is exciting to speculate that manipulation of the adipokine milieu has the potential to influence the severity of acute pancreatitis.

Reg genes are CCK2 receptor targets in ElasCCK2 mice pancreas

We previously demonstrated that expression of the gastrin receptor, CCK2R, in pancreatic acini of transgenic ElasCCK2 mice induced alteration of acinar morphology and differentiation, increased sensitivity to a carcinogen and development of preneoplastic lesions and tumours. Reg proteins are suggested to be involved in pancreatic cancer and in regeneration of endocrine pancreas. Reg I gene is a known target of gastrin. We examined whether an expression of CCK2R in the pancreatic acini of ElasCCK2 mice is linked to induction of Reg proteins expression. We analyzed Reg expression by Western-blot and immunohistochemistry in pancreas from ElasCCK2 and control mice. Islet neogenesis, glucose homeostasis, insulin secretion and content were also evaluated. Reg I is exclusively produced in acini in ElasCCK2 and control mice. In tumoral pancreas, Reg I and Reg III proteins are expressed in duct-like cells in preneoplastic lesions or in the periphery of tumours and in adjacent acini. The expression of Reg III proteins is increased in ElasCCK2 pancreas before the development of preneoplastic lesions in a subpopulation of islet cells and in small islet-like cell clusters dispersed within the acinar tissue. Several criteria of an enhanced neogenesis are fulfilled in ElasCCK2 pancreas. Moreover, ElasCCK2 mice have an improved response to glucose load, an increased insulin secretion and a doubling of insulin content compared to control mice. We show that Reg proteins are targets of CCK2R activation and are induced during early steps of carcinogenesis in ElasCCK2 mice pancreas. Alterations of exocrine tissue homeostasis in ElasCCK2 pancreas concomitantly activate regenerative responses of the endocrine pancreas possibly linked to paracrine actions of Reg III proteins.

Pioglitazone reverses insulin resistance and impaired CCK-stimulated pancreatic secretion in eNOS(-/-) mice: therapy for exocrine pancreatic disorders?

In mice, eNOS (endothelial nitric oxide synthase) maintains in vivo pancreatic secretory responses to carbachol or cholecystokinin octapeptide (CCK-8), maintains insulin sensitivity, and modulates pancreatic microvascular blood flow (PMBF). eNOS(-/-) mice are insulin resistant, and their exocrine pancreatic secretion is impaired. We hypothesized that the reduced exocrine pancreatic secretion in eNOS(-/-) mice is due to insulin resistance or impaired PMBF. To test this hypothesis, we gave eNOS(-/-) and wild-type (WT) mice pioglitazone (20 or 50 mg.kg(-1).day(-1)), an insulin-sensitizing peroxisome proliferator-activated receptor-gamma (PPAR-gamma) activator, and measured pancreatic protein secretion evoked by CCK-8 (160 pmol.kg(-1).h(-1), a maximal stimulus). We also measured insulin resistance, serum glucose, C-peptide, insulin, pancreatic RNA digestive enzyme expression, and PMBF (microsphere technique). In WT mice, pioglitazone did not increase CCK-8-stimulated protein output over baseline. In eNOS(-/-) mice, however, pioglitazone substantially increased the low CCK-8-stimulated protein output that is characteristic of these mutant mice (P < 0.005). Pioglitazone abolished the CCK-8-evoked hyperinsulinemia (P < 0.005) and increased insulin sensitivity of eNOS(-/-) mice (P < 0.05), the latter based on hyperinsulinemic-euglycemic clamp studies. Pioglitazone had no effect on PMBF or pancreas mRNA expression of insulin or digestive enzymes. We conclude that in hyperinsulinemic eNOS(-/-) mice, a nonobese model of insulin resistance relevant to diabetes mellitus and possibly chronic pancreatitis, reduced pancreatic secretion is caused, at least in part, by insulin resistance. Insulin-sensitizing PPAR-gamma agonists such as pioglitazone may thus simultaneously correct endocrine and exocrine pancreatic disorders.

Development and regulation of porcine pancreatic function

A surgical and experimental procedure was developed to enable the collection of pure and inactivated pancreatic juice during the growth of the pig. Studies have shown that, during the suckling period, both the basal and the secretory responses to suckling are low, if present at all. After weaning, basal levels of the total exocrine secretion, total protein, amylase, and trypsin, respectively, increase slightly, while the postprandial levels of total protein, amylase, trypsin, lipase, colipase, and carboxylester lipase, respectively, increase markedly. The pancreatic juice enzyme composition changes qualitatively and the antibacterial activity of the pancreatic juice also significantly increases. Piglet age appeared to be of minor importance, since weaning at either 4 or 6 wk of age gave the same results. Secretin and CCK administered together in supraphysiological doses only significantly affect exocrine function from 3-4 wk of age. However, CCK may also affect the exocrine pancreas indirectly via reflexes initiated intraduodenally. Milk consumption in the suckling pig leads to a postprandial increase in glucose levels but not insulin. Milk appears to be able to regulate the exocrine pancreas to produce only the amount and type of enzymes required for digestion. Thus, milk components or digestive products may affect pancreas function regulation. Studies show that enterostatin, the procolipase activation peptide, may inhibit pancreatic secretion mediated indirectly through the GI tract. Pancreastatin, an endocrine peptide, inhibits both insulin secretion and protein and trypsin secretion to pancreatic juice. In hypoinsulinemic (alloxan+streptozotocin diabetes) pigs (15-20 kg), no postprandial pancreatic juice response is seen, although CCK 33 + secretin can stimulate pancreatic secretion. Hypoinsulinemic pigs have a reduced capacity for glucose tissue utilization, suggesting that tissue metabolism and exocrine pancreas secretion are related.

Enzyme-specific activities and mineral concentrations of the exocrine pancreas from female SHR/N-corpulent (cp) rats

A new rodent model, SHR/N-cp, for study of non-insulin-dependent diabetes mellitus (NIDDM) has recently been developed. The present study reports exocrine pancreatic enzyme activities and mineral concentrations in female corpulent (cp/cp) and lean (+/?) rats fed a diet containing carbohydrate as cooked corn starch or sucrose for 7 months to determine the potential of the model for studies of diet and pancreatic function in NIDDM. Although corpulent female rats weighed 2.5 times more than their lean littermates, they consumed less calories when expressed per 100 g body weight than lean rats. Corpulent rats had a significantly smaller relative pancreatic weight than lean rats (p less than 0.0001), but had greater total pancreatic DNA content and concentration (p less than 0.003) and higher pancreatic amylase (p less than 0.0001), lipase (p less than 0.0011), and chymotrypsinogen (p less than 0.0208) specific activities. Corpulent rats had a significantly lower pancreatic copper concentration than their lean littermates (p less than 0.0193). Corpulent rats consuming starch had a higher pancreatic iron concentration than all other experimental groups (p less than 0.05). The corpulent female rats were only mildly diabetic based upon serum and urine indices. The data suggest that the female SHR/N-corpulent rat may be a useful model for studying exocrine pancreatic function of mild cases of non-insulin-dependent diabetes.

Satiety in the obese Zucker rat: effects of carbohydrate type and acarbose (Bay g 5421)

Despite the obese Zucker rat's hyperphagia on carbohydrate diets such as laboratory chow, this laboratory has found that its satiety response to glucose and other simple sugars is comparable to that of its lean control rat. To further investigate carbohydrate satiety in the Zucker rat, the short-term feeding behavior of obese and lean rats was observed following intragastric infusions (7.2 kcal in 10 ml) of corn starch and the starch hydrolysates Polycose and dextrin. There were no reliable between-genotype differences in the feeding inhibitory effects of Polycose and dextrin. However, in obese rats, the satiety effect of corn starch was delayed and reduced compared to that observed in lean rats (p less than 0.04). To modify the effect of corn starch, rats were administered 0.2 or 0.6 mg/infusion of the carbohydrate digestive inhibitor acarbose (Bay g 5421). Acarbose significantly reduced the satiety effect of corn starch in lean rats (p less than 0.001), and further attenuated satiety in obese rats (p less than 0.02). Since secretion of pancreatic amylase, the enzyme that initiates starch digestion, is decreased in obese rats, this result suggests that alterations of digestive and/or absorptive processes may underlie the obese rat's impaired satiety response to complex carbohydrate.

Translational control of anionic trypsinogen and amylase synthesis in rat pancreas in response to caerulein stimulation

Infusion of rats with optimal doses of caerulein for up to 24 hr resulted in divergent changes in protein synthesis in the exocrine pancreas: a 3-fold increase in synthesis of anionic trypsinogen and a 75% decrease in synthesis of amylase. Lipase synthesis showed no change. Rates of total protein synthesis increased 2-fold, while DNA, RNA, and poly(A)+ mRNA concentrations were unchanged during hormonal stimulation. mRNA concentrations for anionic trypsinogen, lipase, and amylase were determined by dot blot hybridization analysis with cDNA and cRNA probes. Despite 12-fold changes in the ratio of synthesis of anionic trypsinogen to amylase at 24 hr of caerulein stimulation, changes in levels of mRNA encoding these two proteins were not observed. The slight decreases observed in amylase mRNA concentrations were found in both hormone and saline-infused animals. In vitro pulse-chase experiments after 12 hr of saline or caerulein infusion indicated that differential turnover of anionic trypsinogen and amylase did not occur during hormone stimulation. These data demonstrate that the differential regulation observed in protein synthesis that results from a single period of hormone stimulation is mediated by differential regulation of mRNA translation. The high degree of conservation observed in the 5' terminal sequences of both amylase and anionic trypsinogen mRNAs between mouse, rat, and dog suggests that sequence-specific mechanisms and secondary structure may play a role in the translational control of these two mRNAs.

Changes in individual rates of pancreatic enzyme and isoenzyme biosynthesis in the obese Zucker rat

Both alterations of enzyme content and a markedly decreased secretory response to selected physiological stimuli have been demonstrated previously in the pancreas of the obese Zucker rat. The purpose of the present investigation was to determine the degree to which alterations of enzyme content could be attributed to changes in enzyme biosynthesis. Amylase content of obese rats was decreased by 50%, whereas lipase and trypsinogens were significantly increased. However, the decrease in amylase content was less than might have been predicted from the rate of amylase biosynthesis (80% decrease), and the increases in content of trypsinogen(s) and lipase were greater than would have been predicted from alterations in the absolute rates of biosynthesis. In view of the rapid turnover of pancreatic enzymes under normal conditions, it seems probable that a markedly decreased secretory response to various stimuli leads to an increased content of some enzymes in the pancreas of the obese rat. Ciglitazone treatment, which decreases insulin resistance in obese animals and leads to normalization of glucose metabolism in their pancreatic tissue, restored the enzyme-synthesis rates towards normal, showing that the abnormalities of enzyme synthesis were linked to the insulin resistance rather than to the obese genotype itself. Lipid inclusion bodies were found in acinar cells of obese rats. These bodies have previously been described in acinar cells of starved animals, which, in common with the acinar tissue of the obese Zucker rat, have decreased glucose metabolism.