Towards precision medicine for phenylketonuria: The effect of restoring a strict metabolic control in adult patients with early-treated phenylketonuria

BACKGROUND AND OBJECTIVE

Neonatal screening and early treatment have changed the natural history of PKU, preventing severe neurological and intellectual disability. Nevertheless, the outcome of the disease in early-treated adult patients (ETPKU) is less than optimal, the predictive value of metabolic biomarkers is feeble, and the recommended levels of blood phenylalanine (Phe) for adulthood are controversial. A crucial question whose answer will improve our understanding and treatment of PKU is whether cognitive outcomes can be modulated by levels of Phe even in early-treated adults. To address this question, we carried out an interventional study in seven ETPKU women planning a pregnancy.

METHODS

They underwent an extensive neurocognitive assessment at baseline, and 3 and 6 months after having attained the blood Phe concentration recommended to prevent PKU fetopathy, but before pregnancy.

RESULTS

After 3 and 6 months with a stable blood Phe level of about 240 μmol/L, all participants experienced significant improvements in almost all neurocognitive domains and tasks. IQ also increased of 11 to 21 points from the last assessment before enrolment. This pattern remained strong and consistent after correction for multiple comparisons.

CONCLUSION

Our results indicate that a) strong cognitive improvement is possible even in adulthood and may be demonstrated by lowering Phe near normal levels; b) testing cognition under different metabolic conditions may unveil an individual vulnerability to Phe. These results pave the way for personalised treatment of the disease in adults with ETPKU.

Prebiotic Therapy with Inulin Associated with Low Protein Diet in Chronic Kidney Disease Patients: Evaluation of Nutritional, Cardiovascular and Psychocognitive Parameters

A relationship between dysbiotic gut microbiome and chronic kidney disease (CKD) has been recently documented; it contributes to CKD-related complications, including cardiovascular disease. Aim: We tested how a low-protein diet (LPD)-with or without oral inulin supplementation as a prebiotic-modulates some inflammatory, atherosclerosis and endothelial dysfunction indices and nutritional markers, as well as psychocognitive functions in CKD patients. We conducted a prospective, case-control study on CKD patients on conservative therapy, divided in two groups: the intervention group treated with LPD (0.6 g/kg/day) plus inulin (19 g/day) and a control group treated with LPD without inulin, for six consecutive months. Clinical and hematochemical parameters as well as instrumental, and psychocognitive assessments (by SF-36 survey and MMSE, HAM-D, BDI-II) were recorded in all the participants at baseline (T0), at three months (T1) and at six months (T2). A total of 41 patients were enrolled: 18 in the intervention group and 23 in the control group. At T2, in both groups, we observed a significant reduction of serum nitrogen and phosphorus (p ≤ 0.01) and serum uric acid (p ≤ 0.03), and an improvement in metabolic acidosis (bicarbonates, p ≤ 0.01; base excess, p ≤ 0.02). Moreover, at T2 the intervention group showed a reduction in serum insulin (p = 0.008) and fasting glucose levels (p = 0.022), HOMA-IR (p = 0.004), as well as lower total serum cholesterol (p = 0.012), triglycerides (p = 0.016), C-reactive protein (p = 0.044) and homocysteine (p = 0.044) and higher HDL (p < 0.001) with respect to baseline. We also observed a significant amelioration of some quality of life and functional status indices (SF-36 survey) among the intervention group compared to controls, without a significant improvement in the cognitive state (MMSE). On the other hand, an amelioration in mood (by HAM-D and BDI-II) was found in the intervention group and in controls (only by BID-II). In conclusion, LPD in association with oral inulin supplementation improved glycemic and lipid metabolism and ameliorated the systemic inflammatory state, likely reducing cardiovascular risk in CKD patients and this may represent a promising therapeutic option, also improving quality of life and mood.

Adult cognitive outcomes in phenylketonuria: explaining causes of variability beyond average Phe levels

Objective

The objective was to deepen the understanding of the causes of individual variability in phenylketonuria (PKU) by investigating which metabolic variables are most important for predicting cognitive outcomes (Phe average vs Phe variation) and by assessing the risk of cognitive impairment associated with adopting a more relaxed approach to the diet than is currently recommended.

Method

We analysed associations between metabolic and cognitive measures in a mixed sample of English and Italian early-treated adults with PKU (N = 56). Metabolic measures were collected through childhood, adolescence and adulthood; cognitive measures were collected in adulthood. Metabolic measures included average Phe levels (average of median values for each year in a given period) and average Phe variations (average yearly standard deviations). Cognition was measured with IQ and a battery of cognitive tasks.

Results

Phe variation was as important, if not more important, than Phe average in predicting adult outcomes and contributed independently. Phe variation was particularly detrimental in childhood. Together, childhood Phe variation and adult Phe average predicted around 40% of the variation in cognitive scores. Poor cognitive scores (> 1 SD from controls) occurred almost exclusively in individuals with poor metabolic control and the risk of poor scores was about 30% higher in individuals with Phe values exceeding recommended thresholds.

Conclusions

Our results provide support for current European guidelines (average Phe value = < 360 μmol/l in childhood; = < 600 μmo/l from 12 years onwards), but they suggest an additional recommendation to maintain stable levels (possibly Phe SD = < 180 μmol/l throughout life).

Public significance statements

We investigated the relationship between how well people with phenylketonuria control blood Phe throughout their life and their ability to carry out cognitive tasks in adulthood. We found that avoiding blood Phe peaks was as important if not more important that maintaining average low Phe levels. This was particularly essential in childhood. We also found that blood Phe levels above recommended European guidelines was associated with around 30% increase in the risk of poor cognitive outcomes.

Clinical characterization of tremor in patients with phenylketonuria

BACKGROUND

Phenylketonuria (PKU) is due to the deficit of the enzyme phenylalanine hydroxylase, the first step of dopamine synthesis. If not early treated the disease results in severe neurological impairment. Minor neurological signs have been reported in early treated PKU (ETPKU) subjects. Prolactin level is affected by (and reflects) brain dopamine availability. Object of the study was to assess the occurrence, age at onset, distribution, associated neurological signs, and possible pathogenetic biomarkers of tremor in ETPKU.

METHODS

Fifty-nine ETPKU and 43 control subjects (age range 7-54) underwent individual and familiar tremor history, clinical assessment of tremor by means of the Fahn-Tolosa-Marin Tremor Rating Scale, and IQ evaluation. Historical and concomitant biochemical data (blood levels of Phe) and serum prolactin were included in the analysis.

RESULTS

Thirty-two percent of ETPKU patients were affected by postural and kinetic tremor. We found a significant correlation between severity of tremor and: prolactin level at the day of examination (part A: r_s = 0.320; p = .014; part C: r_s = 0.319; p = .014), Phe fluctuations from 12 years onwards (part B: r_s = 0.300; p = .036). We also found a significant correlation between prolactin (18.2 ± 9.6 ng/ml) and Phe levels (852 ± 472 μmol/l) on the day of assessment (r_s = 0.470; p < .001).

CONCLUSIONS

The main clinical features of tremor in ETPKU evoke those of essential tremor, although with a higher prevalence and an earlier onset than in general population. The severity of tremor was related to concomitant prolactin rather than Phe levels. This pattern suggests that metabolic alterations associated with PKU may result in an anticipation of the tremor onset in subjects who are possibly prone to this disorder.

Sarcopenia and cardiovascular risk indices in patients with chronic kidney disease on conservative and replacement therapy

OBJECTIVE

Chronic kidney disease (CKD) is a condition with high cardiovascular mortality associated with emerging risk factors, including sarcopenia. Several mechanisms can affect muscle mass, such as vitamin D deficiency, low protein intake, physical inactivity, metabolic acidosis, and inflammation leading to a worsening of cardiovascular outcomes and cognitive function. We aimed to evaluate the prevalence of sarcopenia in CKD patients on conservative and replacement therapy and the associations between sarcopenia and markers of atherosclerosis, endothelial dysfunction, psychological and cognitive function.

METHODS

We enrolled CKD patients (stage 3/5 KDIGO [Kidney Disease: Improving Global Outcomes]) and hemodialysis, peritoneal dialysis, and post-kidney transplant patients. Clinical, laboratory and instrumental assessments, including bioimpedance analysis, hand-grip strength, intima media thickness, flow-mediated dilation, and epicardial adipose tissue, were performed in addition to analysis of psychological and cognitive status by the Montreal Cognitive Assessment, Mini-Mental State Examination, and Geriatric Depression Scale.

RESULTS

A total of 77 patients (43 male) with a mean age of 69.6 ± 9.85 y were studied. According to validated criteria (using bioimpedance analysis and hand-grip strength), the prevalence of sarcopenia was 49.4%. Sarcopenic patients had higher values of intima media thickness (P = 0.032) and epicardial adipose tissue (P = 0.012) and lower flow-mediated dilation (P = 0.002), total cholesterol (P = 0.005), and high-density lipoprotein cholesterol (P = 0.008) with respect to non-sarcopenic patients. We found higher Geriatric Depression Scale scores (P = 0.04) in sarcopenic patients, whereas we did not find differences between the two groups in Mini-Mental State Examination and Montreal Cognitive Assessment score.

CONCLUSION

Sarcopenia is highly prevalent in CKD/end stage renal disease patients and is associated with changes in early systemic indices of atherosclerosis and endothelial dysfunction, known as markers of worse prognosis.

A new case of malonic aciduria with a presymptomatic diagnosis and an early treatment

Malonyl-CoA decarboxylase deficiency (MLYCD) is a rare autosomal recessive inborn error of metabolism presenting a variable clinical phenotype. We report an affected Italian male receiving an early diagnosis (8days after birth) and a timely dietary therapy (high carbohydrate, low long chain fatty acid and medium chain triglyceride supplemented diet with l-carnitine supplementation). The boy was born at term and presented normal function of the heart (except for a tricuspid Ebstein-like dysplasia) and neurodevelopmental status. Genomic sequencing of MLYCD gene revealed two point mutations (c.672G>A, c.869C>T) not listed in the Human MLYCD Allelic Variant Database nor in Human Gene Mutation Database, responsible for a deleterious effect on protein structure and function according to a computational analysis (MuPro, SIFT, ConSEQ v1.1). At the age of 2years he only showed a mild language and psychomotor delay, while heart functioning became normal. Brain MRI examination was normal. Thirty-five cases, including our patient, have been described to date. This is the first report concerning a malonic aciduria patient diagnosed on newborn screening and treated in a presymptomatic stage of the disease.

THE ETIOLOGY OF HYPERTENSION DUE TO COMPLETE RENAL ISCHEMIA

1. Perfusates of totally ischemic kidneys of cats contain a pressor substance which is not present in the perfusates of normal kidneys, ischemic hind limbs, or ischemic gravid uteri. 2. The pressor material in ischemic renal perfusates originates directly in the kidney as a result of complete ischemia. 3. The pressor principle contained in ischemic renal perfusates is the cause of the hypertension which follows the reestablishment of circulation in completely ischemic kidneys, since perfusates of unreleased completely ischemic kidneys contain more pressor material than perfusates of released ischemic kidneys of the same animal. 4. The pressor principle in ischemic renal perfusates is presumed to be renin for the following reasons, (a) Both substances are destroyed by boiling, (b) Both substances induce tachyphylaxis. (c) The configuration of both pressor curves is identical, (d) The pressor action of both is not reversed by 933F, proving they are not epinephrine-like substances. (e) When incubated with plasma, both form a heat-stable pressor substance. (f) The pressor effect of both is uninfluenced by a previous injection of cocaine, (g) Unreleased, completely ischemic kidneys yield more pressor material on extraction than do released ischemic kidneys of the same animal. 5. The perfusates of blood-free ischemic kidneys contain more renin than those of blood-filled ischemic kidneys. 6. A method is described by which the power of various substances to inhibit or enhance the production of renin in the ischemic kidney may be tested. 7. A small amount of the heat-stable pressor substance, presumably angiotonin or hypertensin, is formed by the reaction of the pressor material (renin) and plasma in the vessels of the kidney during the period of complete ischemia.