Truncation of Pik3r1 causes severe insulin resistance uncoupled from obesity and dyslipidaemia by increased energy expenditure.

OBJECTIVE: Insulin signalling via phosphoinositide 3-kinase (PI3K) requires PIK3R1-encoded regulatory subunits. C-terminal PIK3R1 mutations cause SHORT syndrome, as well as lipodystrophy and insulin resistance (IR), surprisingly without fatty liver or metabolic dyslipidaemia. We sought to investigate this discordance. METHODS: The human pathogenic Pik3r1 Y657∗ mutation was knocked into mice by homologous recombination. Growth, body composition, bioenergetic and metabolic profiles were investigated on chow and high-fat diet (HFD). We examined adipose and liver histology, and assessed liver responses to fasting and refeeding transcriptomically. RESULTS: Like humans with SHORT syndrome, Pik3r1WT/Y657∗ mice were small with severe IR, and adipose expansion on HFD was markedly reduced. Also as in humans, plasma lipid concentrations were low, and insulin-stimulated hepatic lipogenesis was not increased despite hyperinsulinemia. At odds with lipodystrophy, however, no adipocyte hypertrophy nor adipose inflammation was found. Liver lipogenic gene expression was not significantly altered, and unbiased transcriptomics showed only minor changes, including evidence of reduced endoplasmic reticulum stress in the fed state and diminished Rictor-dependent transcription on fasting. Increased energy expenditure, which was not explained by hyperglycaemia nor intestinal malabsorption, provided an alternative explanation for the uncoupling of IR from dyslipidaemia. CONCLUSIONS: Pik3r1 dysfunction in mice phenocopies the IR and reduced adiposity without lipotoxicity of human SHORT syndrome. Decreased adiposity may not reflect bona fide lipodystrophy, but rather, increased energy expenditure, and we suggest that further study of brown adipose tissue in both humans and mice is warranted.

Assessment of calcitonin response to experimentally induced hypercalcemia in cats.

OBJECTIVE: To characterize the dynamics of calcitonin secretion in response to experimentally induced hypercalcemia in cats. ANIMALS: 13 healthy adult European Shorthair cats. PROCEDURES: For each cat, the calcitonin response to hypercalcemia (defined as an increase in ionized calcium concentration > 0.3 mM) was investigated by infusing calcium chloride solution and measuring circulating calcitonin concentrations before infusion (baseline) and at various ionized calcium concentrations. Calcitonin expression in the thyroid glands of 10 of the cats was investigated by immunohistochemical analysis. RESULTS: Preinfusion baseline plasma calcitonin concentrations were very low in many cats, sometimes less than the limit of detection of the assay. Cats had a heterogeneous calcitonin response to hypercalcemia. Calcitonin concentrations only increased in response to hypercalcemia in 6 of 13 cats; in those cats, the increase in calcitonin concentration was quite variable. In cats that responded to hypercalcemia, calcitonin concentration increased from 1.3 ± 0.3 pg/mL at baseline ionized calcium concentration to a maximum of 21.2 ± 8.4 pg/mL at an ionized calcium concentration of 1.60 mM. Cats that did not respond to hypercalcemia had a flat calcitonin-to-ionized calcium concentration curve that was not modified by changes in ionized calcium concentration. A significant strong correlation (r = 0.813) was found between the number of calcitonin-positive cells in the thyroid gland and plasma calcitonin concentrations during hypercalcemia. CONCLUSIONS AND CLINICAL RELEVANCE: Healthy cats had very low baseline plasma calcitonin concentrations. A heterogeneous increase in plasma calcitonin concentration in response to hypercalcemia, which correlated with the expression of calcitonin-producing cells in the thyroid, was identified in cats.

Avaliação da hipercalcemia assintomática em pacientes ambulatoriais / Assessment of asymptomatic hypercalcemia in outpatients

Introdução: Dosagens indiscriminadas de cálcio sérico podem levar à detecção de pacientes assintomáticos, com hipercalcemia, em que o hiperparatireoidismo primário é a causa mais comum. Objetivo: Discutir aforma de avaliação da hipercalcemia detectada em população atendida em regime ambulatorial, avaliando a sua freqüência, com ênfase na pesquisa de hiperparatireoidismo primário. Material e métodos: Foi realizado estudo prospectivo envolvendo 1.049 indivíduos, de 40 a 60 anos, com dosagens séricas de cálcio e albumina, e calculado o valor de cálcio corrigido. Na presença de elevação do cálcio corrigido,foram dosados cálcio iônico, fósforo, paratormônio (PTH) e calciúria. Resultados: A idade foi 49,7 ± 13,7anos e 188 (17,9%) indivíduos apresentaram valores elevados de cálcio corrigido. Desses, 90 pacientescompareceram à segunda avaliação e 19 (2%) mantiveram quadro de hipercalcemia. Os níveis de cálcio iônico (média: 1,2 ± 0,01 mmol/l) foram normais em todos os indivíduos. A calciúria foi 185,8 ± 111,8 mg/24 horas. Os níveis de PTH (média: 46 ± 11,8 pg/ml) foram elevados em três casos, com cintilografia de paratireóides normal. Discussão: A queda na freqüência de hipercalcemia com base novalor do cálcio corrigido e, sobretudo, após dosagem de cálcio ionizável sugere que a dosagem de cálcio livre seja preferida como triagem. Na população estudada não foi diagnosticado hiperparatireoidismo, sugerindo distribuição variável da doença em diferentes populações. Conclusão: Deve ser questionada a dosagem rotineira de cálcio sérico em indivíduos sem quadro clínico que indique a necessidade darealização desse exame. Quando realizada, a dosagem de cálcio iônico deverá ser preferida.

Introduction: Indiscriminate serum calcium measurement may lead to the identification of asymptomatic patientswith hypercalcaemia, which is caused mostly by primary hyperparathyroidism. Objective: To discuss the frequencyof hypercalcaemia and the type of assessment of this condition in an outpatient population, with emphasis on the investigation of primary hyperparathyroidism. Material and methods: In a prospective study 1,049 subjects (age range: 40 to 60 years old) underwent serum calcium and albumin determination and the corrected calcium values were calculated. When there was a rise in the corrected calcium level, ionized calcium, phosphate, parathyroid hormone (PTH) and urinary calcium were measured. Results: The average age was 49.7 ± 13.7 years old, and 188 subjects (17.9%) had elevated corrected calcium levels. Among these, 90 patients underwent the second investigation and 19 (2%) remained hypercalcemic. Ionized calcium levels (average: 1.2 ± 0.01 mmol/L) werenormal in all subjects. Urinary calcium was 185.8 ± 111.8 mg/24 hours. PTH levels (average: 46 ± 11.8 pg/mL)were elevated in three subjects whose parathyroid scintigraphies were normal. Discussion: The fall in the frequencyof hypercalcaemia based on corrected serum calcium levels and mostly after determination of serum ionized calciumsuggests that determinations of serum free calcium are a better screening test. No subject was diagnosed with hyperparathyroidism, what suggests an uneven distribution of the disease in different populations. Conclusion:Routine serum calcium determinations in asymptomatic patients must be questioned. When serum calcium determination is thought necessary, ionized calcium levels should be favored.

Metabolic assessment in patients with urinary lithiasis.

INTRODUCTION: Metabolic investigation in patients with urinary lithiasis is very important for preventing recurrence of disease. The objective of this work was to diagnose and to determine the prevalence of metabolic disorders, to assess the quality of the water consumed and volume of diuresis as potential risk factors for this pathology. PATIENTS AND METHODS: We studied 182 patients older than 12 years. We included patients with history and/or imaging tests confirming at least 2 stones, with creatinine clearance > or = 60 mL/min and negative urine culture. The protocol consisted in the collection of 2, 24-hour urine samples, for dosing Ca, P, uric acid, Na, K, Mg, Ox and Ci, glycemia and serum levels of Ca, P, Uric acid, Na, K, Cl, Mg, U and Cr, urinary pH and urinary acidification test. RESULTS: 158 patients fulfilled the inclusion criteria. Among these, 151 (95.5%) presented metabolic changes, with 94 (62.2%) presenting isolated metabolic change and 57 (37.8%) had mixed changes. The main disorders detected were hypercalciuria (74%), hypocitraturia (37.3%), hyperoxaluria (24.1%), hypomagnesuria (21%), hyperuricosuria (20.2%), primary hyperparathyroidism (1.8%), secondary hyperparathyroidism (0.6%) and renal tubular acidosis (0.6). CONCLUSION: Metabolic change was diagnosed in 95.5% of patients. These results warrant the metabolic study and follow-up in patients with recurrent lithiasis in order to decrease the recurrence rate through specific treatments, modification in alimentary and behavioral habits.

Metabolic assessment in patients with urinary lithiasis

INTRODUCTION: Metabolic investigation in patients with urinary lithiasis is very important for preventing recurrence of disease. The objective of this work was to diagnose and to determine the prevalence of metabolic disorders, to assess the quality of the water consumed and volume of diuresis as potential risk factors for this pathology. PATIENTS AND METHODS: We studied 182 patients older than 12 years. We included patients with history and/or imaging tests confirming at least 2 stones, with creatinine clearance > 60 mL/min and negative urine culture. The protocol consisted in the collection of 2, 24-hour urine samples, for dosing Ca, P, uric acid, Na, K, Mg, Ox and Ci, glycemia and serum levels of Ca, P, Uric acid, Na, K, Cl, Mg, U and Cr, urinary pH and urinary acidification test. RESULTS: 158 patients fulfilled the inclusion criteria. Among these, 151 (95.5 percent) presented metabolic changes, with 94 (62.2 percent) presenting isolated metabolic change and 57 (37.8 percent) had mixed changes. The main disorders detected were hypercalciuria (74 percent), hypocitraturia (37.3 percent), hyperoxaluria (24.1 percent), hypomagnesuria (21 percent), hyperuricosuria (20.2 percent), primary hyperparathyroidism (1.8 percent) secondary hyperparathyroidism (0.6 percent) and renal tubular acidosis (0.6). CONCLUSION: Metabolic change was diagnosed in 95.5 percent of patients. These results warrant the metabolic study and follow-up in patients with recurrent lithiasis in order to decrease the recurrence rate through specific treatments, modification in alimentary and behavioral habits.

Increased resting energy expenditure in subjects with Emery-Dreifuss muscular dystrophy.

We have studied changes in energy expenditure and body composition in adult males with Emery-Dreifuss muscular dystrophy, age-matched males with hyperCKemia and age-matched healthy controls. All participants were studied twice, 2-3 years apart. Resting energy expenditure was studied by indirect calorimetry, lean body mass and body fat by dual X-ray absorptiometry, and muscle mass was estimated based on 24-h urinary creatinine excretion. At baseline and 2-3 years later, body fat was significantly higher (P < 0.011 and P < 0.003, respectively) and lean body mass significantly lower (P < 0.024 and P < 0.012, respectively) in patients with Emery-Dreifuss muscular dystrophy as compared to subjects with hyperCKemia and healthy controls. Resting energy expenditure, over the study period, increased significantly in patients with Emery-Dreifuss muscular dystrophy (P < 0.031), but not in patients with hyperCKemia nor in healthy controls. Our study suggests that patients with Emery-Dreifuss muscular dystrophy may have increased energy expenditure relative to healthy subjects. If not met by increased caloric intake, this greater energy expenditure may partially contribute to a further deterioration in their muscle performance.

Assessment of cellular expression of parathyroid hormone-related protein mRNA and protein in multiple myeloma.

The capacity of multiple myeloma cells to generate parathyroid hormone-related protein (PTHrP) has been examined by in situ assessment of PTHrP mRNA and PTHrP protein in myeloma cells of patients in whom the disease was associated with the development of hypercalcaemia. The presence of PTHrP mRNA was evaluated by in situ hybridization using an antisense riboprobe, and PTHrP by immunohistochemistry using a monoclonal antibody, in archival bone marrow trephine specimens from 17 patients. PTHrP mRNA was detected in myeloma cells in 16 of the 17 patients, indicating a high frequency of PTHrP gene expression in myeloma cells in these subjects. PTHrP protein was, on the other hand, detected in the myeloma cells of only five of these patients. The impact of the mercury-based fixation and decalcification procedure used for processing the bone marrow trephine specimens was assessed to determine the influence of this process on the outcome of the immunohistochemical assay for PTHrP. It was shown that this preparative procedure resulted in a marked reduction of immunohistochemically detectable PTHrP, which provides a possible explanation for the lower frequency of positivity for PTHrP in myeloma cells in the bone marrow specimens. The present findings are consistent with the view that PTHrP can be generated in myeloma cells in vivo, and could contribute to osteolysis and hypercalcaemia, as in patients with cancer.

Direct and indirect assessment of the parathyroid hormone response to pamidronate therapy in Paget's disease of bone and hypercalcaemia of malignancy.

In patients with either Paget's disease or hypercalcaemia associated with malignancy (HCM) we have assessed the parathyroid response to pamidronate therapy, both by immunoassay of serum intact parathyroid hormone PTH (1-84) and by measurement of indirect parameters of PTH bioactivity, tubular maximum reabsorption of phosphate (TmPO4/GFR) and nephrogenous cyclic AMP (NcAMP). In 12 patients with Paget's disease, therapy with pamidronate produced a small but significant decrease in adjusted serum calcium within the reference interval which was accompanied by a progressive increase in PTH (1-84) secretion and a corresponding fall in TmPO4/GFR and increase in NcAMP. In 12 patients with HCM pretreatment, PTH (1-84) concentrations were suppressed, whilst mean TmPO4/GFR was reduced and NcAMP was increased, compatible in most patients, with parathyroid hormone-related peptide (PTHrP) driven hypercalcaemia. Therapy with pamidronate produced the expected fall in serum calcium but caused an increase in PTH (1-84) secretion in the presence of absolute hypercalcaemia. The initial subnormal TmPO4/GFR decreased further to a nadir on day 5, and there was a corresponding further increase in NcAMP. By day 7, however, when PTH (1-84) concentrations were maximal, there was a significant paradoxical rise in TmPO4/GFR and a corresponding decrease in NcAMP. These data are consistent with a variable trigger point for PTH (1-84) secretion, one consequence of which is a reduction in the risk of hypocalcaemia following pamidronate. The results have major clinical implications for the interpretation of PTH (1-84) measurements in patients who are being treated or about to be treated for bone disease or for hypercalcaemia of malignancy (HCM).(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of renal and skeletal components of hypercalcemia.

The management of hypercalcemia of malignancy is guided by assessments of its various components. Since the intestine usually makes no contribution to hypercalcemia under these circumstances, the problem is to measure the net efflux of calcium out of bone and the ability of the kidneys to excrete the unwanted calcium load. Established relationships between serum and urinary calcium excretion rates allow the quantitation of the relative contribution of an impaired glomerular filtration rate, of reduced renal tubular calcium reabsorption, and of increased bone resorption. Since the renal handling of calcium is closely related to that of sodium in the proximal nephron, the rate of sodium excretion is an important variable in these measurements. A practical approach to the separation of hypercalcemia into its renal and skeletal components is described in this article. Examples of how these measurements can be used to assess the responses to various types of therapy for malignancy-associated hypercalcemia are also given.

[Assessment of the calcium homeostatic state using the double calcium tolerance test]. / Otsenka sostoianiia gomeostaza kal'tsiia s pomoshch'iu sdvoennogo kal'tsii-tolerantnogo testa.

An acute tolerance test per os using calcium (Ca) lactate at a dose of 0.25 mmol of Ca per kg of body mass (calcium tolerance test--CTT) was performed twice in healthy persons (HP) and in patients with chronic heart failure (CHF) of various degrees: before and after 3-day administration of the same dose of Ca lactate. The "double" CTT made it possible to detect in HP and CHF a "phenomenon of adaptation" to Ca excess in the body based probably on changes in the activity of calcium-regulating hormones. It was manifested in less marked and prolonged tolerance hypercalcemia and a more rapid and effective calciuretic reaction, and probably in decreased intestinal absorption of Ca. It pointed to reversibility of Ca metabolic derangements even in severe CHF and a possibility of their non-medicamentous correction.

Influence of urinary sodium excretion on the clinical assessment of renal tubular calcium reabsorption in hypercalcaemic man.

The relation between urinary sodium excretion (NaE) and renal tubular calcium reabsorption (TmCa/GFR) was assessed in patients with hypercalcaemia associated with malignancy and primary hyperparathyroidism. On acute saline loading of seven normally hydrated patients with primary hyperparathyroidism and five patients with malignancy, raised values of TmCa/GFR were reduced to normal in most cases, in association with increases in NaE. The reduction in TmCa/GFR, which occurred, may have been due to a reduction in proximal tubular calcium reabsorption associated with sodium: this would have obscured the effect of humorally mediated increases in distal tubular calcium reabsorption, which are stimulated either by parathyroid hormone or by a putative humoral mediator in hypercalcaemia of malignancy. In patients who were normally hydrated NaE and TmCa/GFR were not significantly correlated. When data were included from patients who were dehydrated and from those undergoing acute saline loading, significant inverse correlations between NaE and TmCa/GFR were observed both in primary hyperparathyroidism (r = -0.49; p less than 0.02) and malignancy (r = -0.60; p less than 0.001). In clinical practice changes in TmCa/GFR associated with sodium seem to be of minor importance under normal circumstances, but they become evident at the upper and lower extremes of urinary sodium excretion. In clinical studies of renal calcium handling urinary sodium excretion must also be assessed, as interpreting TmCa/GFR data is difficult in states of excessive sodium loading or depletion.

Assessment of calcium homeostasis in the critically ill surgical patient. The diagnostic pitfalls of the McLean-Hastings nomogram.

Hypocalcemia is a common problem in critically ill surgical patients. We prospectively evaluated whether measurement of the total serum calcium (Ca) concentration or calculation of the serum ionized Ca level (by the McLean-Hastings nomogram) accurately reflects the measured serum ionized Ca level. Although 71% and 58% of 156 predominantly surgical intensive care unit (ICU) patients were hypocalcemic by the total serum Ca or calculated ionized Ca level, respectively, only 12% were hypocalcemic by directly measured serum ionized Ca measurement. The total serum Ca and calculated ionized Ca concentrations were sensitive (95% and 89%, respectively) but lacked specificity (32% and 46%, respectively) in predicting ionized hypocalcemia. Analyses of Ca binding to albumin in the serum of surgical ICU patients and normal subjects suggested that there is a circulating factor in critically ill patients that increases the binding of Ca to albumin. These observations may explain why the McLean-Hastings nomogram underestimates the protein-induced changes in serum Ca in critically ill surgical subjects. We conclude that: total serum Ca and calculated ionized Ca concentrations are poor indicators of the true serum ionized Ca status in critically ill surgical patients, and we recommend direct measurement of serum ionized Ca levels in these patients; and variability in the affinity of Ca for binding proteins in critical illness may explain the poor correlation between serum total and ionized Ca measurements.

Asymptomatic hyperparathyroidism: an assessment of operative intervention.

The incidental finding of hypercalcaemia during multi-channel screening was the initiating event in 33 (45 per cent) of 79 consecutive cases of surgically treated primary hyperparathyroidism. This subgroup was asymptomatic as defined. Although significant biochemical differences existed between symptomatic and asymptomatic cases, a range of metabolic indices of bone turnover fell postoperatively in almost all asymptomatic subjects, although initially abnormal in only 35 per cent. Achievement of normocalcaemia was significantly surgeon-dependent.