Differential diagnosis of familial diabetes insipidus

Renal water transport in health and disease

Saving body water by optimal reabsorption of water filtered by the kidney leading to excretion of urine with concentrations of solutes largely above that of plasma allowed vertebrate species to leave the aquatic environment to live on solid ground. Filtered water is reabsorbed for 70% and 20% by proximal tubules and thin descending limbs of Henle, respectively. These two nephron segments express the water channel aquaporin-1 located along both apical and basolateral membranes. In the proximal tubule, the paracellular pathway accounts for at least 30% of water reabsorption, and the tight-junction core protein claudin-2 plays a key role in this permeability. The ascending limb of Henle and the distal convoluted tubule are impermeant to water and are responsible for urine dilution. The water balance is adjusted along the collecting system, i.e. connecting tubule and the collecting duct, under the control of arginine-vasopressin (AVP). AVP is synthesized by the hypothalamus and released in response to an increase in extracellular osmolality or stimulation of baroreceptors by decreased blood pressure. In response to AVP, aquaporin-2 water channels stored in subapical intracellular vesicles are translocated to the apical plasma membrane and raise the water permeability of the collecting system. The basolateral step of water reabsorption is mediated by aquaporin-3 and -4, which are constitutively expressed. Drugs targeting water transport include classical diuretics, which primarily inhibit sodium transport; the new class of SGLT2 inhibitors, which promotes osmotic diuresis and the non-peptidic antagonists of the V2 receptor, which are pure aquaretic drugs. Disturbed water balance includes diabetes insipidus and hyponatremias. Diabetes insipidus is characterized by polyuria and polydipsia. It is either related to a deficit in AVP secretion called central diabetes insipidus that can be treated by AVP analogs or to a peripheral defect in AVP response called nephrogenic diabetes insipidus. Diabetes insipidus can be either of genetic origin or acquired. Hyponatremia is a common disorder most often related to free water excess relying on overstimulated or inappropriate AVP secretion. The assessment of blood volume is key for the diagnosis and treatment of hyponatremia, which can be classified as hypo-, eu-, or hypervolemic.

The Efficacy of Targeted Perioperative Management for Diabetic Patients with Traumatic Calcaneal Fractures

Objective

To assess the efficacy of targeted perioperative management for diabetic patients with traumatic calcaneal fractures.

Methods

Between April 2020 and December 2020, 100 diabetic patients with traumatic calcaneal fractures treated in our institution satisfying the inclusion criteria were enrolled and assigned to receive either conventional treatment with surgery or plaster fixation (observation group) or targeted treatment with surgery or plaster fixation (experimental group) via the random number table method, with 50 patients in each group. All eligible patients were followed up for 1 year postoperatively. Outcome measures included length of hospital stay, recovery time, fracture healing, duration of postoperative wound drainage, complication rate, blood glucose, and treatment satisfaction. The Maryland score was used for the assessment of foot function.

Results

The duration of postoperative wound drainage, length of hospital stay, and recovery time in the experimental group (3.63 ± 1.04 d, 12.13 ± 3.77 d, and 111.22 ± 16.24 d) were significantly shorter than those in the observation group (5.71 ± 2.34 d, 15.28 ± 4.42 d, 123.10 ± 22.82 d) (P < 0.01). The experimental group obtained a markedly higher complete healing rate versus the observation group (P < 0.001). A significantly lower complication rate was observed in the experimental group than in the observation group (P < 0.05). The Maryland scores results were dichotomized into good (≥75 points) and poor (<75 points). The experimental group showed significantly higher Maryland scores good rate and treatment satisfaction versus the observation group (P < 0.01). The experimental group patients were associated with better postoperative fasting glucose and 2 h postprandial glucose versus those in the observation group (P < 0.05).

Conclusion

Targeted treatment in the perioperative management of diabetic patients with traumatic calcaneal fractures significantly promotes the recovery of patients, reduces the incidence of complications, increases treatment satisfaction, and ameliorates the doctor-patient relationship.

A Novel Form of Familial Vasopressin Deficient Diabetes Insipidus Transmitted in an X-linked Recessive Manner

CONTEXT

Familial pituitary diabetes insipidus has been described only in an autosomal dominant or recessive mode of inheritance.

OBJECTIVE

This work aims to determine the cause of a novel form of familial diabetes insipidus (DI) that is controlled by desmopressin therapy but segregates in an X-linked recessive manner.

METHODS

Thirteen members from 3 generations of the kindred with familial DI were studied. Water intake, urine volume, urine osmolality, plasma osmolality, and plasma vasopressin were measured under basal conditions, during fluid deprivation, 3% saline infusion, and water loading. Magnetic resonance images of the posterior pituitary also were obtained. In affected males, the effects of desmopressin therapy and linkage of the DI to markers for chromosome Xq28 were determined. In addition, the genes encoding vasopressin, aquaporin-2, the AVPR2 receptor, and its flanking regions were sequenced.

RESULTS

This study showed that 4 males from 3 generations of the kindred have DI that is due to a deficiency of vasopressin, is corrected by standard doses of desmopressin, and segregates with markers for the AVPR2 gene in Xq28. However, no mutations were found in AVPR2 or its highly conserved flanking regions. Exome sequencing confirmed these findings and also revealed no deleterious variants in the provasopressin and aquaporin-2 genes. The 4 obligate female carriers osmo-regulated vasopressin in the low normal range.

CONCLUSION

X-linked recessive transmission of DI can be due to a defect in either the secretion or the action of vasopressin. Other criteria are necessary to differentiate and manage the 2 disorders correctly.

Complementary Role of Oxytocin and Vasopressin in Cardiovascular Regulation

The neurons secreting oxytocin (OXY) and vasopressin (AVP) are located mainly in the supraoptic, paraventricular, and suprachiasmatic nucleus of the brain. Oxytocinergic and vasopressinergic projections reach several regions of the brain and the spinal cord. Both peptides are released from axons, soma, and dendrites and modulate the excitability of other neuroregulatory pathways. The synthesis and action of OXY and AVP in the peripheral organs (eye, heart, gastrointestinal system) is being investigated. The secretion of OXY and AVP is influenced by changes in body fluid osmolality, blood volume, blood pressure, hypoxia, and stress. Vasopressin interacts with three subtypes of receptors: V1aR, V1bR, and V2R whereas oxytocin activates its own OXTR and V1aR receptors. AVP and OXY receptors are present in several regions of the brain (cortex, hypothalamus, pons, medulla, and cerebellum) and in the peripheral organs (heart, lungs, carotid bodies, kidneys, adrenal glands, pancreas, gastrointestinal tract, ovaries, uterus, thymus). Hypertension, myocardial infarction, and coexisting factors, such as pain and stress, have a significant impact on the secretion of oxytocin and vasopressin and on the expression of their receptors. The inappropriate regulation of oxytocin and vasopressin secretion during ischemia, hypoxia/hypercapnia, inflammation, pain, and stress may play a significant role in the pathogenesis of cardiovascular diseases.