Complex carbohydrate malabsorption in exocrine pancreatic insufficiency

Nutritional Therapy in Chronic Pancreatitis

Malnutrition is a frequent complication in patients with chronic pancreatitis. Maldigestion as a consequence of pancreatic exocrine insufficiency is the major cause of malnutrition in these patients. Together with that, toxic habits and alterations of the gastroduodenal transit may play a relevant role. Malnutrition in chronic pancreatitis is associated with osteoporosis, sarcopenia, poor quality of life, and increased mortality. An adequate nutritional evaluation including anthropometric, biochemical, and morphologic parameters is recommended in these patients. Nutritional advice and support together with an adequate pancreatic enzyme replacement therapy are indicated.

Metabolic markers of protein maldigestion after a 15N test meal in minipigs with pancreatic exocrine insufficiency

The effect of pancreatic exocrine insufficiency (PEI) on protein malabsorption is little documented, partly due to methodological barriers. We aimed to validate biomarkers of protein malabsorption using a ¹⁵N test meal in a minipig model of PEI. Six pancreatic duct-ligated minipigs were used as a model of PEI and four nonoperated animals as a control. All animals were equipped with an ileocecal reentrant cannula. Minipigs were given a test meal containing [¹⁵N]casein. The PEI animals repeated the test three times, in the absence of any pancreatic enzymes, or after pancreatic substitution at two levels [ A or B: 7,500 or 75,000 (lipase) and 388 or 3881 (protease) FIP U]. Ileal chyme, urine, and blood were collected postprandially. Nitrogen and ¹⁵N were measured in digestive and metabolic pools. We obtained a gradient of ileal protein digestibility from 29 ± 11% in PEI to 89 ± 6% in the controls and a dose- dependent response of enzymes. Insulin and gastric inhibitory polypeptide secretions were decreased by PEI, an effect that was counteracted with the enzymes at level B. The total recovery of ¹⁵N in urinary urea and plasma proteins was 14 ± 5.1% in the control group and decreased to 5.5 ± 2.1% by PEI. It was dose dependently restored by the treatment. Both ¹⁵N recovery in plasma and urine were correlated to protein digestibility. We confirm that the ¹⁵N transfer in those pools is a sensitive marker of protein malabsorption. Nevertheless, an optimization of the test meal conditions would be necessary in the view of implementing a clinical test. NEW & NOTEWORTHY We designed an intervention study to create a gradient of ileal protein digestibility in minipigs with pancreatic exocrine insufficiency and to validate reliable metabolic markers using a ¹⁵N oral meal test. ¹⁵N recovery in plasma proteins and to a higher extent in urine was sensitive to protein malabsorption. This test is minimally invasive and could be used to reveal protein malabsorption in patients.

Yarrowia lipolytica Lipase 2 Is Stable and Highly Active in Test Meals and Increases Fat Absorption in an Animal Model of Pancreatic Exocrine Insufficiency

BACKGROUND & AIMS

Pancreatic exocrine insufficiency (PEI) reduces pancreatic secretion of digestive enzymes, including lipases. Oral pancreatic enzyme replacement therapy (PERT) with pancreatin produces unsatisfactory results. The lipase 2 produced by the yeast Yarrowia lipolytica (YLLIP2; GenBank: AJ012632) might be used in PERT. We investigated its ability to digest triglycerides in a test meal and its efficacy in reducing fecal fat in an animal model of PEI.

METHODS

YLLIP2 was produced by genetically engineered Y lipolytica and purified from culture media. YLLIP2 or other gastric (LIPF) and pancreatic (PNLIPD) lipases were added to a meal paste containing dietary triglycerides, at a range of pH values (pH 2-7), with and without pepsin or human bile and incubated at 37°C. We collected samples at various time points and measured lipase activities and stabilities. To create an animal model of PEI, steatorrhea was induced by embolization of the exocrine pancreas gland and pancreatic duct ligation in minipigs. The animals were given YLLIP2 (1, 4, 8, 40, or 80 mg/d) or pancreatin (100,000 US Pharmacopeia lipase units/d, controls) for 9 days. We then collected stool samples, measured fat levels, and calculated coefficient of fat absorption (CFA) values.

RESULTS

YLLIP2 was highly stable and poorly degraded by pepsin, and had the highest activity of all lipases tested on meal triglyceride at pH 4-7 (pH 6 with bile: 94 ± 34 U/mg; pH 4 without bile: 43 ± 13 U/mg). Only gastric lipase was active and stable at pH 3, whereas YLLIP2 was sensitive to pepsin hydrolysis after pH inactivation. From in vitro test meal experiments, the lipase activity of YLLIP2 (10 mg) was estimated to be equivalent to that of pancreatin (1200 mg; 100,000 US Pharmacopeia units) at pH 6. In PEI minipigs, CFA values increased from 60.1% ± 9.3% before surgery to 90.5% ± 3.2% after administration of 1200 mg pancreatin (P < .05); CFA values increased to a range of 84.6% ± 3.0% to 90.0% ± 3.8% after administration of 4-80 mg YLLIP2 (P < .05).

CONCLUSIONS

The yeast lipase YLLIP2 is stable and has high levels of activity against test meal triglycerides in a large pH range, with and without bile. Oral administration of milligram amounts of YLLIP2 significantly increased CFA values, similar to that of 1.2 g pancreatin, in a minipig model of PEI.

Starch Origin and Thermal Processing Affect Starch Digestion in a Minipig Model of Pancreatic Exocrine Insufficiency

Although steatorrhea is the most obvious symptom of pancreatic exocrine insufficiency (PEI), enzymatic digestion of protein and starch is also impaired. Low praecaecal digestibility of starch causes a forced microbial fermentation accounting for energy losses and meteorism. To optimise dietetic measures, knowledge of praecaecal digestibility of starch is needed but such information from PEI patients is rare. Minipigs fitted with an ileocaecal fistula with (n = 3) or without (n = 3) pancreatic duct ligation (PL) were used to estimate the rate of praecaecal disappearance (pcD) of starch. Different botanical sources of starch (rice, amaranth, potato, and pea) were fed either raw or cooked. In the controls (C), there was an almost complete pcD (>92%) except for potato starch (61.5%) which was significantly lower. In PL pcD of raw starch was significantly lower for all sources of starch except for amaranth (87.9%). Thermal processing increased pcD in PL, reaching values of C for starch from rice, potato, and pea. This study clearly underlines the need for precise specification of starch used for patients with specific dietetic needs like PEI. Data should be generated in suitable animal models or patients as tests in healthy individuals would not have given similar conclusions.

The malabsorption of commonly occurring mono and disaccharides: levels of investigation and differential diagnoses

BACKGROUND

Adverse food reactions (AFR) have has recently attracted increased attention from the media and are now more commonly reported by patients. Its classification, diagnostic evaluation, and treatment are complex and present a considerable challenge in clinical practice. Non-immune-mediated types of food intolerance have a cumulative prevalence of 30% to 40%, while true (immune-mediated) food allergies affect only 2% to 5% of the German population.

METHOD

We selectively searched the literature for pertinent publications on carbohydrate malabsorption, with special attention to published guidelines and position papers.

RESULTS

Carbohydrate intolerance can be the result of a rare, systemic metabolic defect (e.g., fructose intolerance, with a prevalence of 1 in 25,000 persons) or of gastrointestinal carbohydrate malabsorption. The malabsorption of simple carbohydrates is the most common type of non-immune-mediated food intolerance, affecting 20% to 30% of the European population. This condition is caused either by deficient digestion of lactose or by malabsorption of fructose and/or sorbitol. Half of all cases of gastrointestinal carbohydrate intolerance have nonspecific manifestations, with a differential diagnosis including irritable bowel syndrome, intolerance reactions, chronic infections, bacterial overgrowth, drug side effects, and other diseases. The diagnostic evaluation includes a nutritional history, an H2 breath test, ultrasonography, endoscopy, and stool culture.

CONCLUSION

The goals of treatment for carbohydrate malabsorption are to eliminate the intake of the responsible carbohydrate substance or reduce it to a tolerable amount and to assure the physiological nutritional composition of the patient's diet. In parallel with these goals, the patient should receive extensive information about the condition, and any underlying disease should be adequately treated.

An overview of the diagnosis and management of nutrition in chronic pancreatitis

Chronic pancreatitis is characterized by long-standing inflammation of the pancreas, which results in fibrosis and the gradual loss of pancreatic function. The loss of islets and acinar cells results in diabetes and exocrine insufficiency, respectively. Exocrine insufficiency can result in maldigestion of fat, protein, and carbohydrate as well as vitamins and minerals. Patients may present with variable severity of disease, from mild to severe. The diagnosis of chronic pancreatitis can be challenging, especially in patients with early or mild disease who have few to no morphologic abnormalities on standard abdominal imaging studies. A number of imaging modalities and tests have evolved to aid in the diagnosis of chronic pancreatitis based on changes in structure or function. Clinicians typically focus on treating pain in chronic pancreatitis as opposed to exocrine insufficiency, despite the fact that maldigestion and malabsorption can result in nutrition deficiencies. The aims of this review are to describe the various modalities used to diagnose chronic pancreatitis, to illustrate the nutrition deficiencies associated with exocrine insufficiency, and to provide an overview of nutrition assessment and treatment in these patients.

Colonic energy salvage in chronic pancreatic exocrine insufficiency

BACKGROUND

Chronic pancreatic exocrine insufficiency results in maldigestion. As a result, increased amounts of undigested nutrients reach the colon, providing more substrate for bacterial fermentation to produce short-chain fatty acids, which could therefore provide additional energy supplement.

METHODS

This study aimed to assess carbohydrate malabsorption in patients with chronic pancreatic exocrine insufficiency after ingestion of a standard diet and to calculate energy salvaged by colonic bacterial metabolism. A 72-hour stool collection was done on 10 adult patients receiving a 3-day standard diet containing 100 g fat, 329 g carbohydrate, and 154 g protein, and short-chain fatty acids, fat, carbohydrate, and nitrogen excretion were assessed. A breath hydrogen test after ingestion of 200 g (dry weight) cooked maize meal (test meal) and 10 g oral inulin (standard), respectively, was subsequently done on the patients and 15 healthy adult controls.

RESULTS

Breath hydrogen production after ingestion of maize meal and inulin, respectively, and calculated carbohydrate malabsorption were significantly greater in patients (21.4% +/- 17%) than in controls (10.2 +/- 1.4%; p < .05). Patients malabsorbed 70.4 g/d (281.6 kcal) carbohydrate in the standard diet. Total carbohydrate loss in stool amounted to 8.1 g/d (2.4%), and 62.3 g/d (19%) was hence salvaged as short-chain fatty acids for energy provision. Colonic bacterial fermentation therefore converted 88.5% of malabsorbed carbohydrate to short-chain fatty acids, 92.8% of which was absorbed and 7.2% excreted. This suggests that 10.2% of energy expenditure/requirement in these patients is derived from salvage of malabsorbed carbohydrate.

CONCLUSIONS

Colonic bacterial metabolism is a significant source of energy salvage in patients with pancreatic enzyme deficiency.

Human pancreatic digestive enzymes

A primary function of the pancreas is to produce digestive enzymes that are delivered to the small intestine for the hydrolysis of complex nutrients. Much of our understanding of digestive enzymes comes from studies in animals. New technologies and the availability of the sequence of the human genome allow for a critical review of older reports and assumptions based on animal studies. This report updates our understanding of human pancreatic digestive enzymes with a focus on new insights into the biology of human proteases, lipases and amylases.

Comparison of inulin and lactulose as reference standards in the breath hydrogen test assessment of carbohydrate malabsorption in patients with chronic pancreatic exocrine insufficiency

Although often used as a reference standard in the breath hydrogen test (BHT), lactulose fermentation produces more hydrogen, compared to starch, and may therefore not be ideal. This study compares inulin with lactulose as reference standard in the study of carbohydrate malabsorption. Seventeen patients with malabsorption due to chronic pancreatitis and 15 normal controls were studied. Following overnight fasts, BHTs were performed after ingesting 10 g lactulose, 10 g inulin, and 200 g (16 g highly resistant starch) maize meal. Lactulose fermentation produced significantly more hydrogen than inulin in patients with malabsorption (97 +/- 20 vs 45 +/- 22 ppm x hr; P < 0.05) and controls (43 +/- 18 vs 21 +/- 10 ppm x hr; P < 0.05). Patients produced more hydrogen than controls with both standards (lactulose, 97 +/- 20 vs 43 +/- 18 ppm x hr, P < 0.05; inulin 45 +/- 22 vs 21 +/- 10 ppm x hrs; P < 0.05), suggesting adaptation of the colonic flora. Calculated CHO malabsorption was 2.5 +/- 0.8 vs 5.2 +/- 3.8 g with lactulose and 5.2 +/- 3.1 vs 11.2 +/- 9.6 g with inulin as standards in controls and patients, respectively (P < 0.05). Lactulose produces more breath hydrogen than inulin. Calculation of CHO malabsorption using these standards is therefore not comparable.

Hydrogen breath test with low-dose rice flour for assessment of exocrine pancreatic insufficiency

OBJECTIVES

The hydrogen (H2) breath test is widely used in the assessment of carbohydrate malabsorption. Severe exocrine pancreatic insufficiency markedly diminishes pancreatic amylase production and results in malabsorption of complex carbohydrates. Thus, the H2 breath test with low-dose rice flour starch was tested to determine its value in detecting exocrine pancreatic insufficiency by comparison with a direct measurement of pancreatic function.

METHODS

Ten patients with clinically suspected pancreatic insufficiency confirmed with a duodenal perfusion technique and measurement of trypsin and lipase output after cerulein stimulation were included. An H2-rice flour breath test was performed by orally administering 30 g of rice flour. End-alveolar breath samples were obtained before rice load and at 30-minute intervals thereafter for the next 5 hours.

RESULTS

The results are expressed as median (percentile 25-75). Patients included 8 men and 2 women with moderate to severe exocrine pancreatic insufficiency due to chronic pancreatitis, pancreatectomy, or cystic fibrosis. Stimulated duodenal output of lipase and trypsin was abnormally low in all patients (median release, 1.7; range, 0.5-4.5 and 0.8, range, 0.1-11.3 KU/h, respectively). Basal H2 excretion was 9 ppm (range, 7-17) and delta increase over basal H2 excretion was 4 ppm (range, 1-6). Correlation between H2-rice breath test and basal or stimulated duodenal output of lipase and trypsin was not significant.

CONCLUSION

In exocrine pancreatic insufficiency, an oral load of 30 g rice flour slightly raises H2 excretion in breath. This increase is not useful for detecting pancreatic insufficiency due to poor sensitivity and because it is influenced by extrapancreatic factors such as small bowel bacterial overgrowth.