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BACKGROUND HIV protease inhibitors have been shown to worsen glucose and lipid metabolism. Recent studies have suggested that protease inhibitors can impair insulin secretion in HIV-infected patients. We studied the effects of the protease inhibitor combination lopinavir and ritonavir on insulin secretion, insulin sensitivity, and lipid metabolism in HIV-negative persons. METHODS A combination dose of lopinavir 400 mg and ritonavir 100 mg was given twice daily to eight HIV-seronegative men for 4 weeks. Fasting glucose, insulin, lipid, and lipoprotein profiles; oral glucose tolerance; insulin secretion and insulin-mediated glucose disposal by hyperglycemic clamp; and body composition by dual energy X-ray absorptiometry were determined before and after lopinavir/ritonavir administration. RESULTS There was no change in first-phase insulin secretion (2.82 +/- 0.30 versus 2.71 +/- 0.31 nmol/l; P = 0.60), as well as fasting insulin and glucose levels, oral glucose tolerance, or insulin-mediated glucose disposal after 4 weeks administration of lopinavir/ritonavir. However, there were significant increases in fasting triglycerides (1.02 +/- 0.13 versus 2.20 +/- 0.31 mmol/l; P = 0.001), total cholesterol (4.42 +/- 0.30 versus 5.70 +/- 0.60 mmol/l; P = 0.007), and apo B-100 levels (0.86 +/- 0.07 versus 1.07 +/- 0.11 g/l; P = 0.0009). High-density lipoprotein cholesterol decreased (0.99 +/- 0.11 versus 0.82 +/- 0.10 mmol/l; P = 0.005). There were no changes in body composition, weight, or body fat. CONCLUSION Although administration of lopinavir/ritonavir to healthy, HIV-seronegative volunteers for 4 weeks resulted in increased triglyceride and decreased high-density lipoprotein cholesterol levels, there was no change in first-phase insulin secretion during the hyperglycemic clamp. The reported effects of protease inhibitor on insulin secretion in HIV-infected individuals may be due to changes in HIV-related factors and not a direct drug effect.

Nephrogenic systemic fibrosis (NSF) is a disease of thickened, hard, hyperpigmented skin lesions with or without systemic fibrosis occurring in patients with renal insufficiency and associated with the administration of gadolinium-containing contrast. The pathogenesis of this disease is unclear, and there is no definitive treatment. We describe a 71-yr-old patient with stable chronic lymphocytic leukemia (CLL), end-stage renal disease (ESRD), and NSF who presented with hypercalcemia in 2006. Before onset of renal insufficiency in 2002, serum calcium, phosphorus, and PTH levels were normal. In 2004, the patient began hemodialysis, and he was diagnosed with NSF in 2005, shortly after undergoing an MRI with gadolinium contrast administration. Over the next 6 mo, albumin-corrected serum total calcium levels rose from 9.9 to 13.1 mg/dl (normal range, 8.5-10.5 mg/dl) with normal serum phosphorus levels. On admission in September 2006, 1,25-dihydroxyvitamin D [1,25(OH)(2)D] levels were elevated at 130.7 pg/ml (normal range, 25.1-66.1 pg/ml). Biopsy of an NSF lesion showed increased 25-hydroxyvitamin D(3)-1-alpha hydroxylase (CYP27B1) immunostaining compared with the biopsy from a normal control. This is the first reported association of NSF with hypercalcemia caused by elevated 1,25(OH)(2)D levels. This metabolic disturbance should be sought in future cases to determine a connection between NSF, 1,25(OH)(2)D metabolism, and CYP27B1 activation in the skin, which may shed light on the pathogenesis of this unusual local and systemic fibrosing disorder.

We have used site-directed mutagenesis to probe the structural requirements for catalysis and dimerization of human hepatic methionine adenosyltransferase (hMAT). We built a homology model of the dimeric hMAT III inferred by the crystal structure of the highly homologous Escherichia coli MAT dimer. The active sites of both enzymes comprise the same amino acids and are located in the inter-subunit interface. All of the amino acids predicted to be in the hMAT III active site were mutated, as well as residues in a conserved ATP binding region. All of the mutations except one severely affected catalytic activity. On the other hand, dimerization was affected only by single mutations of three different residues, all on one monomer. The homology model suggested that the side chains of these residues stabilized the monomer and participated in a bridge between subunits consisting of a network of metal and phosphate ions. In agreement with this observation, we demonstrated that dimerization cannot occur in the absence of phosphate.

Background: Some HIV protease inhibitors (PIs), including full-dose ritonavir (800 mg) and ritonavir-boosted lopinavir, acutely induce insulin resistance in the absence of HIV infection and changes in body composition. Boosting dose ritonavir (100-200 mg) is the most commonly prescribed PI, yet its effects on glucose metabolism have not been described in the absence of another PI. Methods: In this randomized, double-blind, cross-over study, a single dose of ritonavir 200 mg or placebo was given to healthy HIV-seronegative volunteers before assessment of insulin sensitivity by euglycemic hyperinsulinemic clamp. Results: Boosting dose ritonavir had no effect on insulin-mediated glucose disposal (M/I, placebo: 8.59 +/- 0.83 vs. ritonavir: 8.51 +/- 0.64 mg/kg per minute per mu U/mL insulin, P = 0.89). Conclusions: A single boosting dose of ritonavir does not alter insulin sensitivity, suggesting lopinavir is likely responsible for the induction of insulin resistance demonstrated in prior short-term studies of lopinavir/ritonavir. There is a dose-dependent effect of ritonavir on insulin sensitivity.

People with HIV infection have metabolic abnormalities that resemble metabolic syndrome (hypertriglyceridemia, low high-density lipoprotein cholesterol, and insulin resistance), which is known to predict increased risk of cardiovascular disease (CVD). However, there is not one underlying cause for these abnormalities and they are not linked to each other. Rather, individual abnormalities can be affected by the host response to HIV itself, specific HIV drugs, classes of HIV drugs, HIV-associated lipoatrophy, or restoration to health. Furthermore, one component of metabolic syndrome, increased waist circumference, occurs less frequently in HIV infection. Thus, HIV infection supports the concept that metabolic syndrome does not represent a syndrome based on a common underlying pathophysiology. As might be predicted from these findings, the prevalence of CVD is higher in people with HIV infection. It remains to be determined whether CVD rates in HIV infection are higher than might be predicted from traditional risk factors, including smoking.

Summary Methionine adenosyltransferase (MAT) I/III deficiency, caused by mutations in the MAT1A gene, is characterized by persistent hypermethioninemia without elevated homocysteine or tyrosine. Clinical manifestations are variable and poorly understood, although a number of individuals with homozygous null mutations in MAT1A have neurological problems, including brain demyelination. We analyzed MAT1A in seven hypermethioninemic individuals, to provide insight into the relationship between genotype and phenotype. We identified six novel mutations and demonstrated that mutations resulting in high plasma methionines may signal clinical difficulties. Two patients—a compound heterozygote for truncating and severely inactivating missense mutations and a homozygote for an aberrant splicing MAT1A mutation—have plasma methionine in the 1,226–1,870 μM range (normal 5–35 μM) and manifest abnormalities of the brain gray matter or signs of brain demyelination. Another compound heterozygote for truncating and inactivating missense mutations has 770–1,240 μM plasma methionine and mild cognitive impairment. Four individuals carrying either two inactivating missense mutations or the single-allelic R264H mutation have 105–467 μM plasma methionine and are clinically unaffected. Our data underscore the necessity of further studies to firmly establish the relationship between genotypes in MAT I/III deficiency and clinical phenotypes, to elucidate the molecular bases of variability in manifestations of MAT1A mutations.