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Ethylmalonic/adipic aciduria: effects of oral medium-chain triglycerides, carnitine, and glycine on urinary excretion of organic acids, acylcarnitines, and acylglycines.

A 9-y-old girl with ethylmalonic/adipic aciduria was hospitalized to determine the possible therapeutic efficacy of oral carnitine and glycine supplementation. To provoke a mild metabolic stress, her diet was supplemented with 440 mg/kg/d of medium-chain triglycerides. She was treated successively with carnitine (100 mg/kg/d) for 5 d, neither carnitine nor glycine for 2 d, and then glycine (250 mg/kg/d) for 6 d. Consecutive 12-h urine collections were obtained throughout the entire period. The urinary excretion of eight organic acids, four acylglycines, and four acylcarnitines, which accumulate as a result of a metabolic block of five mitochondrial acyl-CoA dehydrogenases, were quantitatively determined by capillary gas chromatography, stable isotope dilution gas chromatography/mass spectrometry, and radioisotopic exchange HPLC, respectively. The excretion of each group of metabolites was calculated as the mean percentage of total output (mumol/24 h) during the four phases of the protocol (organic acids/acylglycines/acylcarnitines = 100.0%): 1) regular diet (3 d); 88.1/10.8/1.1; 2) medium-chain triglyceride supplementation (4); 82.5/15.6/1.9; 3) medium-chain triglycerides plus carnitine (5); 79.2/8.2/12.6; and 4) medium-chain triglycerides plus glycine (6); 81.0/18.7/0.3. Comparison between total and individual excretion of acylglycines and acylcarnitines indicates that oral glycine supplementation enhanced the conjugation and excretion of fatty acyl-CoA intermediates as efficiently as carnitine. We propose that oral glycine supplementation should be considered in the treatment of other inborn errors of metabolism associated with abnormal urinary excretion of acylglycines.

Acylation↗

Moderate caloric restriction, but not physiological hyperleptinemia per se, enhances mitochondrial oxidative capacity in rat liver and skeletal muscle--tissue-specific impact on tissue triglyceride content and AKT activation.

The study aimed at determining, in lean tissues from nonobese rats, whether physiological hyperleptinemia with leptin-induced reduced caloric intake and/or calorie restriction (CR) per se: 1) enhance mitochondrial-energy metabolism gene transcript levels and oxidative capacity; and 2) reduce triglyceride content. Liver and skeletal muscles were collected from 6-month-old Fischer 344 rats after 1-wk leptin sc infusion (0.4 mg/kg . d: leptin + approximately 3-fold leptinemia vs. ad libitum-fed control) or moderate CR (-26% of those fed ad libitum) in pair-fed animals (CR). After 1 wk: 1) leptin and CR comparably enhanced transcriptional expression of mixed muscle mitochondrial genes (P < 0.05 vs. control); 2) CR independently increased (P < 0.05 vs. leptin-control) hepatic mitochondrial-lipooxidative gene expression and oxidative capacity; 3) hepatic but not muscle mitochondrial effects of CR were associated (P < 0.01) with increased activated insulin signaling at AKT level (P < 0.05 vs. leptin-control); 4) liver and muscle triglyceride content were comparable in all groups. In additional experiments, assessing time course of posttranscriptional CR effects, 3-wk superimposable CR (P < 0.05): 1) increased both liver and muscle mitochondrial oxidative capacity; and 2) selectively reduced muscle triglyceride content. Thus, in nonobese adult rat: 1) moderate CR induces early increments of mitochondrial-lipooxidative gene expression and time-dependent increments of oxidative capacity in liver and mixed muscle; 2) sustained moderate CR alters tissue lipid distribution reducing muscle but not liver triglycerides; 3) mitochondrial-lipid metabolism changes are tissue-specifically associated with hepatic AKT activation; 4) short-term physiological hyperleptinemia has no independent stimulatory effects on muscle and liver mitochondrial-lipooxidative gene expression. Increased lean tissue oxidative capacity could favor substrate oxidation over storage during reduced nutrient availability.

Animals↗

Effect of amiodarone on serum lipids, lipoprotein lipase, and hepatic triglyceride lipase.

We have determined the effects of chronic amiodarone treatment on lipid metabolism and compared them with those of hypothyroidism in the rat. Serum triglyceride was lower in both amiodarone-treated and hypothyroid rats; total cholesterol was higher in hypothyroid rats, and serum high density lipoprotein cholesterol remained unchanged. Amiodarone increased adipose tissue lipoprotein lipase activity. Hepatic triglyceride lipase activity was decreased in both hypothyroid and amiodarone-treated groups. The effects of amiodarone on serum triglyceride and adipose tissue lipoprotein lipase were reversed by concomitant administration of T3. The activity of hepatic triglyceride lipase, however, was not increased. Our findings indicate that amiodarone causes marked changes in lipid metabolism which are similar to those found in hypothyroidism.

Adipose Tissue↗

Improved triglycerides and insulin sensitivity with 3 months of acipimox in human immunodeficiency virus-infected patients with hypertriglyceridemia.

CONTEXT: Metabolic abnormalities such as hypertriglyceridemia remain a challenge for optimizing long-term health in HIV-infected patients. OBJECTIVE: Elevation of free fatty acids (FFAs) may contribute to hyperlipidemia and insulin resistance in HIV. We evaluated the efficacy and safety of chronic inhibition of lipolysis in HIV-infected men and women with hypertrigyceridemia. We hypothesized that acipimox would lead to significant reductions in triglycerides and improved insulin sensitivity, compared with placebo. DESIGN: A 3-month, randomized, double-blind, controlled trial of acipimox (250 mg thrice daily) vs. placebo was conducted in 23 HIV-infected men and women with hypertriglyceridemia (>150 mg/dl), abnormal fat distribution, and no current lipid-lowering therapy. The primary outcome variable was triglyceride concentration, and insulin sensitivity measured by hyperinsulinemic euglycemic clamp was a secondary outcome. SETTING: The study was conducted at an academic medical center. RESULTS: Acipimox resulted in significant reductions in FFAs [mean change -0.38 (0.06) vs. 0.08 (0.06) mEq/liter with placebo, -68 vs. +17% change from mean baseline, P < 0.0001], decreased rates of lipolysis (P < 0.0001), and a median triglyceride decrease from 238 mg/dl at baseline to 190 mg/dl, compared with an increase from 290 to 348 mg/dl in the placebo group (P = 0.01). Acipimox improved insulin sensitivity [acipimox +2.31 (0.74) vs. placebo -0.21 (0.90) mg glucose per kilogram lean body mass per minute, or +31 vs. -2% change from mean baseline values, P = 0.04]. Improvements in insulin sensitivity were significantly correlated with reductions in FFAs (r = -0.62, P = 0.003) and lipolysis (r = -0.59, P = 0.005). CONCLUSIONS: Acipimox resulted in significant sustained reductions in lipolysis, improved glucose homeostasis, and significant but modest reductions in triglycerides in HIV-infected individuals with abnormal fat distribution and hypertriglyceridemia. Improvement in overall metabolic profile with acipimox suggests a potential clinical utility for this agent that requires further investigation.

Adult↗

Comparison of the lymphatic transport of a lipophilic drug from vehicles containing alpha-tocopherol and/or triglycerides in rats.

The applicability of alpha-tocopherol as a lymphotropic carrier for a highly lipophilic drug has been evaluated. Transport to the intestinal lymph of the highly lipophilic model drug, Lu28-179, in rats after administration to the stomach in an alpha-tocopherol emulsion was compared with lymphatic transport after administration of a sesame oil emulsion and an alpha-tocopherol/sesame oil emulsion. Lymphatic transport of the triglycerides and of alpha-tocopherol was determined. A conscious rat model was used, and the mesenteric lymph was collected. There was no significant difference between the cumulative masses of triglyceride from the two emulsions containing triglyceride 24 h after administration. Administration of an alpha-tocopherol emulsion seemed to induce mobilization of endogenous triglyceride. The lymphatic transport of alpha-tocopherol was less than 1 mg 24 h after administration of both emulsions containing alpha-tocopherol. The absorption of Lu28-179 from the alpha-tocopherol emulsion was very low, with a lymphatic recovery of 0.05%. When administered in an alpha-tocopherol/sesame oil emulsion, the recovery of Lu28-179 increased sevenfold to 0.35%. However, after administration of Lu28-179 in a sesame oil emulsion, the lymphatic recovery increased a further 13-fold to 4.5%. In conclusion, the study showed that alpha-tocopherol did not promote lymphatic absorption of Lu28-179 and thus was not a good lymphotropic carrier, as compared with sesame oil. Alpha-tocopherol in combination with sesame oil was not a good lymphotropic carrier either. The non-absorbed alpha-tocopherol fraction in the intestine might be able to prevent the absorption of Lu28-179.

Administration, Oral↗

Vasospastic angina in patients with systemic triglyceride storage disease with Jordans' anomaly and cardiomyopathy.

Vasospastic angina was demonstrated clinically and angiographically in a 54-year-old patient with systemic triglyceride storage disease and cardiomyopathy. He and his younger sister had been diagnosed in 1985 as having systemic triglyceride storage with Jordans' anomaly. In 1993, he began complaining of rest and effort chest pain in the morning, which was accompanied by ST depression by ECG. Sublingual nitroglycerine was effective for treating this pain. Intracoronary injection of acetylcholine induced severe coronary vasoconstriction in the left anterior descending artery. Left ventricular contraction was diffusely impaired. Deposits of numerous triglyceride droplets and a decrease in the density of myofibrils in cardiocytes were found in the specimens obtained by endomyocardial biopsy. The impaired left ventricular contraction may have been due to the changes in myocardial cells. His sister complained of a similar chest pain that was completely controlled by calcium channel antagonis. Thus, our cases demonstrated vasospastic angina associated with cardiomyopathy secondary to systemic triglyceride storage disease with Jordans' anomaly, though the causal relationship between these conditions remains unclear.

Adult↗

Lower plasma triglyceride level in Syrian hamsters fed on skim milk fermented with Lactobacillus casei strain Shirota.

The effect of fermented skim milk (FSM) by Lactobacillus casei strain Shirota on plasma lipids in hamsters was examined. Hamsters fed on cholesterol-free and -enriched diets containing 30% FSM had lower levels of plasma triglyceride than those fed on the control diet. In the experiment with the cholesterol-enriched diet-fed hamsters, the plasma triglyceride level was suppressed by FSM at concentrations of 10% to 30%. Unfermented milk tended to lower the level of triglyceride, but not significantly. The plasma cholesterol concentration was not affected by an FSM and unfermented skim milk supplement to the diet. L. casei strain Shirota grew well in the presence of mixed lipid micelles containing bile acid, but did not have the ability to remove cholesterol from the culture broth. These results indicate that FSM lowered the plasma triglyceride level in hamsters.

Animals↗

Attenuated response of the serum triglyceride concentration to ingestion of a chocolate containing polydextrose and lactitol in place of sugar.

We examined the effects of ingesting a non-sugar chocolate containing polydextrose and lactitol in place of sucrose and lactose on the concentrations of plasma glucose and serum insulin and triglyceride in humans. A regular chocolate was used as the control. A crossover study was employed, and the subjects each ingested 46 g of the control or non-sugar chocolate in the experiments. Alterations in the blood components were monitored for a period of 150 min after ingestion. The control chocolate elevated the concentrations of plasma glucose and serum insulin, with the peak occurring 30 min after ingestion, but the non-sugar chocolate had a very minor effect. The serum triglyceride concentration gradually increased after ingesting the control chocolate, but was only slightly elevated 150 min after ingesting the non-sugar chocolate. An animal study also showed an attenuated response of serum triglyceride to the administration of a fat emulsion containing polydextrose and lactitol, suggesting that the triglyceride transit through the gut was promoted by these compounds. These results suggest that, compared to regular chocolate, fat absorption in the gut was less after ingesting the non-sugar chocolate, presumably resulting in less effect on body fat deposition.

Adult↗

Hemodynamic, respiratory, and metabolic effects of medium-chain triglyceride-enriched lipid emulsions following valvular heart surgery.

STUDY: A lipid emulsion containing 10 percent medium-chain triglycerides (MCT) and 10 percent long-chain triglycerides (LCT) was infused at a rate of 1 ml/kg/h (3.3 mg/kg/min) for 2 h, in 12 patients (2 males, 10 females; mean age, 54 +/- 3 (SEM) years; range, 34 to 67 years) 24 h after open-heart surgery (mitral valve replacement). METHODS: Hemodynamic factors (pulmonary and radial artery indwelling catheters), oxygen and carbon dioxide partial pressures, oxygen saturation, oxygen delivery and consumption, and intrapulmonary shunt fraction were obtained before, during, and after lipid infusion (for 2 h), at 30-s intervals, along with some metabolic indexes (triglycerides, free fatty acids, glucose, insulin, lactate, acetoacetate). RESULTS: No statistically significant changes in heart rate, cardiac index, systemic and pulmonary pressures and resistances, central venous and pulmonary capillary pressures, or arterial oxygen partial pressure were observed during infusion. Arterial carbon dioxide partial pressure values were constantly reduced throughout and after the end of lipid infusion, as compared with baseline values, while oxygen consumption was increased significantly without any change in oxygen delivery. No adverse effects on intrapulmonary shunt fraction were observed. Statistically significant increases of triglycerides, free fatty acids, acetoacetate and insulin (peak values at end of the lipid infusion) were found in comparison with baseline values. Plasma glucose increased significantly during lipid infusion and remained higher than baseline values until the end of the study. Lactate levels were unchanged except for a slight decrease at the end of the study, without any derangement of acid-base equilibrium. Neither arrhythmias nor adverse clinical reactions were observed as a consequence of lipid infusion. CONCLUSIONS: Fat emulsions containing both MCT and LCT, when given at 3.3 mg/kg/min for 120 min following valvular heart surgery, do not exert negative cardiopulmonary effects, and could represent a source of rapidly metabolized substrates.

Acetoacetates↗

Process development for production of medium chain triglycerides using immobilized lipase in a solvent-free system.

The synthesis of tricaprylin, tricaprin, trilaurin, and trimyristin in a solvent-free system was conducted by mixing a commercial immobilized lipase with the organic reagents (glycerol and fatty acid) in a 20-mL batch reactor with constant stirring. The effects of temperature, fatty acid/glycerol molar ratio, and enzyme concentration on the reaction conversion were determined. The reactions were carried out for 26 h and the nonpolar phase was analyzed by gas chromatography. Appreciable levels of medium chain triglycerides were achieved, except for tricaprylin. The higher selectivity values for the production of triglycerides were attained under the following conditions: a fatty acid/glycerol molar ratio of 5; enzyme concentration of 5 or 9% (w/w); and temperatures of 70 degrees C (tricaprin), 80 degrees C (trilaurin), and 90 degrees C (trimyristin). After completion of the esterification reaction under these conditions, the recovery of the triglyceride and fatty acids, and the reusability of the enzyme were studied. The unreacted fatty acid and the produced triglyceride were satisfactorily recovered. The commercial immobilized lipase was used in 10 consecutive batch reactions at 80 degrees C, with 100% selectivity in the trilaurin and trimyristin synthesis. The possibility of enzyme reuse and the recovery of residual fatty acid are relevant results that contribute to increasing the viability of the process.

Anion Exchange Resins↗

Quantitative determination of faecal fatty acids and triglycerides by Fourier transform infrared analysis with a sodium chloride transmission flow cell.

We studied the applicability of Fourier transform infrared (FTIR) spectroscopy to determine the amount of faecal fatty acids and triglycerides in faeces. For this, we have optimised a simple hexane extraction procedure of stool. After extraction, an aliquot of the hexane layer is directly injected into the measurement cell of the spectrophotometer and absorbance at 1714 cm(-1) and 1751 cm(-1) is read for quantitation of fatty acids and triglycerides, respectively. Comparison of the FTIR spectrophotometric method with the traditional titrimetric Van de Kamer method for faecal fat determination showed a good correlation. The advantage of our method over the previously described FTIR and near-infrared spectroscopy (NIR) methods is that it allows a combined measurement of both fatty acids and triglycerides in one run, using a simple and rapid hexane extraction procedure. Clinical validation of this method was performed by reviewing the medical records of 24 patients with steatorrhoea: patients with pancreatic steatorrhoea showed highly increased faecal triglyceride excretion, but a normal faecal fatty acid and faecal weight when compared with patients with non-pancreatic intestinal steatorrhoea.

Adult↗

Triglyceride pools, flight and activity variation at the Gpdh locus in Drosophila melanogaster.

We have created a set of P-element excision-derived Gpdh alleles that generate a range of GPDH activity phenotypes ranging from zero to full activity. By placing these synthetic alleles in isogenic backgrounds, we characterize the effects of minor and major activity variation on two different aspects of Gpdh function: the standing triglyceride pool and glycerol-3-phosphate shuttle-assisted flight. We observe small but statistically significant reductions in triglyceride content for adult Gpdh genotypes possessing 33-80% reductions from normal activity. These small differences scale to a notable proportion of the observed genetic variation in triglyceride content in natural populations. Using a tethered fly assay to assess flight metabolism, we observed that genotypes with 100 and 66% activity exhibited no significant difference in wing-beat frequency (WBF), while activity reductions from 60 to 10% showed statistically significant reductions of approximately 7% in WBF. These studies show that the molecular polymorphism associated with GPDH activity could be maintained in natural populations by selection in the triglyceride pool.

Animals↗

Elevated serum triglycerides with clozapine resolved with risperidone in four patients.

Serum triglyceride levels of four patients with psychotic disorders were decreased after switching therapy from clozapine to risperidone. In two patients clozapine was reinstated after risperidone was discontinued; serum triglyceride levels increased. This increase when clozapine was switched to risperidone and vice versa is consistent with our previous report of elevated serum triglyceride levels in clozapine-treated patients. Other reports show increases with the atypical antipsychotics, olanzapine and quetiapine. We believe serum triglyceride levels should be monitored in patients who have other cardiac risk factors and are receiving clozapine.

Adult↗

Ovariectomy decreases plasma triglyceride levels and both prevents and alleviates glomerular disease in uninephrectomized female analbuminemic rats.

Female Nagase analbuminemic rats (NAR) are profoundly hypertriglyceridemic and develop proteinuria and glomerulosclerosis when aging and after uninephrectomy (UNX). Ovariectomy (OVX) markedly decreases plasma triglyceride levels in this species. This study evaluated whether decreasing triglyceride levels by OVX could prevent renal disease or alleviate its progression in UNX female NAR. Female NAR underwent OVX at 0, 12, 24, or 36 wk after UNX. In the absence of OVX, the animals developed progressive proteinuria from 18 wk after UNX and showed extensive glomerular sclerosis, lipid deposition, and hypertrophy at euthanasia (49 wk after UNX). These changes were prevented by OVX carried out at 0 or 12 wk, and attenuated by OVX at 24 wk after UNX. If performed at 36 wk after UNX, OVX had no effect on glomerulosclerosis, although it reduced proteinuria. In 95% (20 of 21) of the rats with proteinuria over 10 mg/day, proteinuria decreased in the first 6 wk after OVX. The percentage decrease in proteinuria correlated inversely with the glomerulosclerosis score at euthanasia (r = -0.58, P < 0.01). OVX had no effect on hyperfiltration and hyperperfusion in the UNX rats. OVX consistently reduced plasma triglyceride levels in rats both with and without proteinuria, and it also reduced plasma cholesterol, but only in conjunction with reduction in proteinuria. It was concluded that OVX in UNX female NAR prevents glomerulosclerosis if performed before proteinuria and attenuates further development of established renal disease if performed in a timely manner. This study's data suggest that in UNX female NAR, the lowering of plasma triglyceride levels plays a central role in the renoprotective action of OVX.

Aging↗

The ATGL gene is associated with free fatty acids, triglycerides, and type 2 diabetes.

Adipose triglyceride lipase (ATGL) was recently described to predominantly perform the initial step in triglyceride hydrolysis and therefore seems to play a pivotal role in the lipolytic catabolism of stored fat in adipose tissue. In the first study investigating genetic variations within the ATGL gene in humans, 12 polymorphisms identified via sequencing and database search were studied in 2,434 individuals of European ancestry from Utah. These polymorphisms and their haplotypes were analyzed in subjects not taking diabetes medication for association with plasma free fatty acids (FFAs) as primary analysis, as well as triglycerides and glucose as a secondary analysis (n = 1,701, 2,193, or 2,190, respectively). Furthermore, type 2 diabetes (n = 342 of 2,434) was analyzed as an outcome. FFA concentrations were significantly associated with several single nucleotide polymorphisms (SNPs) of ATGL (P values from 0.015 to 0.00003), consistent with additive inheritance. The pattern was similar when considering triglyceride concentrations. Furthermore, two SNPs showed associations with glucose levels (P < 0.00001) and risk of type 2 diabetes (P < 0.05). Haplotype analysis supported and extended the shown SNP association analyses. These results complement previous findings of functional studies in mammals and elucidate a potential role of ATGL in pathways involved in components of the metabolic syndrome.

Adult↗

Treatment with artificial beta-cell decreases very-low-density lipoprotein triglyceride synthesis in type I diabetes.

The effect of restoration of euglycemia with the artificial beta-cell (Biostator GCIIS) on triglyceride metabolism was studied in seven normolipidemic patients with type I diabetes mellitus. Very-low-density lipoprotein triglyceride (VLDL-TG) transport was determined with [3H]glycerol as an endogenous precursor of VLDL-TG; the resultant kinetic data were evaluated by multicompartmental analysis. Studies of triglyceride metabolism were performed in diabetic patients taking their usual dose of subcutaneous insulin (control study) and after 72 h of euglycemia with the artificial beta-cell (Biostator study). Treatment with the artificial beta-cell resulted in a decrease in mean (+/- SE) 24-h plasma glucose levels from 199 +/- 9 to 123 +/- 7 mg/dl and an increase in mean plasma free-insulin levels from 12.3 +/- 1.9 to 27.6 +/- 4.2 microU/ml (P less than .05). These changes were accompanied by a decrease in mean plasma TG levels from 134 +/- 29 to 88 +/- 15 mg/dl (P less than .05). Kinetic studies demonstrated that the change in plasma triglyceride levels was primarily due to a decrease in VLDL-TG transport (i.e., synthesis), which fell from 11.7 +/- 2.5 mg X h-1 X kg-1 ideal wt during the control study to 7.5 +/- 2.0 mg X h-1 X kg-1 ideal wt during the Biostator study (P less than .05). There was no significant change in fractional catabolic rates of VLDL-TG between the two studies (0.35 +/- .05 vs. 0.38 +/- .07 h-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Interrelationships among insulin's antilipolytic and glucoregulatory effects and plasma triglycerides in nondiabetic and diabetic patients with endogenous hypertriglyceridemia.

We tested the hypothesis that the previously observed association among hypertriglyceridemia, hyperinsulinemia, and insulin resistance could be explained by a defect in insulin's antilipolytic effect. Insulin action was measured in 10 nondiabetic and 8 diabetic patients with hypertriglyceridemia (fasting plasma triglyceride 800 +/- 154 and 1105 +/- 445 mg/dl, respectively, P NS; fasting plasma glucose 99 +/- 3 and 161 +/- 12 mg/dl, respectively, P less than .001) and in 8 weight-matched normolipemic nondiabetic individuals (fasting plasma triglyceride and glucose 110 +/- 21 and 91 +/- 3 mg/dl). The slope of the decay in plasma free fatty acid (FFA) during insulin infusion was used as an index of insulin's antilipolytic effect. Insulin stimulation of glucose uptake in vivo during intravenous hyperinsulinemic clamp and in vitro in adipocytes were measures of insulin's glucoregulatory action. Both glucoregulatory and antilipolytic effects were similarly reduced in both hypertriglyceridemic groups compared with normal subjects. The plasma triglyceride concentration correlated positively with the slope of FFA suppression by insulin (r = .81, P less than .0001) and the fasting FFA concentration (r = .65, P less than .0001). In multiple linear regression analysis, insulin's antilipolytic effect and the fasting FFA concentration explained 83% of the variation in the plasma triglyceride concentration. These associations were independent of insulin's glucoregulatory effect and the fasting plasma insulin concentration. The data indicate that patients with endogenous hypertriglyceridemia are resistant to both the antilipolytic and glucoregulatory actions of insulin and that increased flux of FFA as a result of the latter, rather than hyperinsulinemia, is responsible for elevation of very-low-density lipoprotein production.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

Genotype/phenotype relationships in HNF-4alpha/MODY1: haploinsufficiency is associated with reduced apolipoprotein (AII), apolipoprotein (CIII), lipoprotein(a), and triglyceride levels.

Hepatocyte nuclear factor (HNF)-4alpha is a transcription factor that plays an important role in regulation of gene expression in pancreatic beta-cells and in the liver. Heterozygous mutations in the HNF-4alpha gene are responsible for maturity-onset diabetes of the young 1 (MODY1), which is characterized by pancreatic beta-cell-deficient insulin secretion. HNF-4alpha is a major transcriptional regulator of many genes expressed in the liver. However, no liver defect has been identified in individuals with HNF-4alpha mutations. In this study, we have identified HNF-4alpha target genes that are mainly expressed in the liver, including alpha1-antitrypsin, alpha1-antichymotrypsin, alpha-fetal protein, ceruloplasmin, IGF binding protein 1, transferrin, apolipoprotein(AI) [apo(AI)], apo(AII), apo(B), and apo(CIII). Serum levels of these proteins and Lp(a) and triglycerides were measured in 24 members of the HNF-4alpha/MODY1 RW pedigree (Q268X mutation), including 12 diabetic patients with HNF-4alpha mutations (D-HNF4+/-), 6 nondiabetic subjects with HNF-4alpha mutations (N-HNF4+/-), 6 normal relatives (N-HNF4+/+), 6 unrelated normal matched control subjects (N-HNF4+/+), and 12 matched diabetic (non-MODY1-5) patients (D-HNF4+/+). Serum levels of apo(AII), apo(CIII), lipoprotein(a) [Lp(a)], and triglyceride were significantly reduced in HNF4+/- subjects (26.9, 19.8, 12.1, and 72.1 mg/dl, respectively) compared with HNF4+/+ subjects (37.4, 26.5, 45.2, and 124.2 mg/dl, respectively) (P = 0.00001, P = 0.01, P = 0.00006, and P = 0.000003, respectively). This reduction was not found when apo(AII), apo(CIII), Lp(a), and triglyceride levels were compared in D-HNF4+/- versus N-HNF4+/- or in D-HNF4+/+ versus N-HNF4+/+ subjects, which indicates that HNF-4alpha haploinsufficiency rather than hyperglycemia is the primary cause of decreased serum protein and triglyceride concentrations. Furthermore, we determined that genetic or environmental modifiers other than HNF-4alpha do not appear to contribute to the observed decrease of HNF-4alpha-regulated serum proteins. This study demonstrates that a heterozygous HNF-4alpha mutation leads to an HNF-4alpha-dependent hepatocyte secretory defect of liver-specific proteins.

Adult↗