Congenital generalized lipodystrophy, or Berardinelli-Seip syndrome (BSCL), is a rare autosomal recessive disease characterized by a near-absence of adipose tissue from birth or early infancy and severe insulin resistance. Other clinical and biological features include acanthosis nigricans, hyperandrogenism, muscular hypertrophy, hepatomegaly, altered glucose tolerance or diabetes mellitus, and hypertriglyceridemia. A locus (BSCL1) has been mapped to 9q34 with evidence of heterogeneity. Here, we report a genome screen of nine BSCL families from two geographical clusters (in Lebanon and Norway). We identified a new disease locus, designated BSCL2, within the 2.5-Mb interval flanked by markers D11S4076 and D11S480 on chromosome 11q13. Analysis of 20 additional families of various ethnic origins led to the identification of 11 families in which the disease cosegregates with the 11q13 locus; the remaining families provide confirmation of linkage to 9q34. Sequence analysis of genes located in the 11q13 interval disclosed mutations in a gene homologous to the murine guanine nucleotide-binding protein (G protein), gamma3-linked gene (Gng3lg) in all BSCL2-linked families. BSCL2 is most highly expressed in brain and testis and encodes a protein (which we have called seipin) of unknown function. Most of the variants are null mutations and probably result in a severe disruption of the protein. These findings are of general importance for understanding the molecular mechanisms underlying regulation of body fat distribution and insulin resistance.

A B ST R A C T The metabolic response to the first fast experienced by all mammals has been studied in the newborn rat. Levels of fuels and hormones have been compared in the fetal and maternal circulations at term. Then, after cesarean section just before the normal time of birth, sequential changes in the same parameters were quantified during the first 16 h of the neonatal period. No caloric intake was permitted, and the newborns were maintained at 370C. Activities of three key hepatic enzymes involved in glucose production were estimated.Marked differences in maternal and fetal hormones and fuels were observed. Lower levels of glucose, free fatty acids, and glycerol but higher levels of lactate, a-amino nitrogen, alanine, and glutamine were present in the fetus. Pyruvate, glutamate, and ketone bodies were not significantly different. The combination of a strikingly higher fetal immunoreactive insulin and a slightly lower immunoreactive glucagon (pancreatic) resulted in a profound elevation in the insulin-to-glucagon ratio, a finding consistent with an organism in an anabolic state.The rat at birth presents a body composition with respect to fuels available for mobilization and conversion which is dominated by carbohydrate and protein, since little fat is present. However, at birth a transient period of hypoglycemia occurred, associated with a rapid fall in insulin and rise in glucagon, causing reversal of the insulin-to-glucagon relationship toward ratios such as were observed in the mother. After a lag period, hepatic activities of phosphorylase, glucose-6-phosphatase, and phosphoenolpyruvate carboxykinase increased. Concurrent with these enzyme changes, the blood glucose returned to levels at or above those of the fetus. Interestingly, the fall observed in levels of the gluconeogenic precursors, lactate and amino acids, preceded the rise in enzyme activities and restoration of blood glucose. After 4 h, however, hypoglycemia recurred, during a period of decreasing hepatic glycogen content and blood lactate, pyruvate, and glycerol levels but of stable or increasing amino acid concentrations. Hepatic gluconeogenesis in this phase of depleted glycogen stores was insufficient to maintain euglycemia.Substrates derived from fat showed early changes of smaller magnitude. The rise in free fatty acids which occurred was less than twofold the value at birth, though this rise persisted up to 6 h. Whereas glycerol rose transiently, acetoacetate did not change and P-hydroxybutyrate concentration fell. Both ketone bodies showed a marked rise at 16 h, at a time of diminished free fatty acid levels. Plasma growth hormone, though higher in the fetal than the maternal circulation, showed no consistent change during the period of observation.The changes in levels of the endocrine pancreatic hormones at birth were appropriate in time, magnitude, and direction to be implicated as prime regulators of the metabolic response during the neonatal period in the rat.

The association of insulin-dependent diabetes mellitus (IDDM) with certain HLA alleles is well documented in pediatric patients. Whether a similar association is found in adult-onset IDDM is not clear, although the disease occurs after the age of 20 in 50% of cases. HLA class II DRB1, DQA1, and DQB1 alleles were studied in 402 type I diabetics and 405 healthy controls (all Caucasian) using oligonucleotide typing after gene amplification. Alleles DRB1 *03, DRB1 *04, DQB1 *0201, DQB1 *0302, DQA1 *0301, and DQA1 *0501 were indeed enriched in diabetics and the highest relative risk was observed in patients carrying both the DRB1 *03-DQB1 *0201 and the DRB1 *0402 or DRB1 *0405-DQB1 *0302 haplotypes. However none of these alleles, or specific residues, could alone account for the susceptibility to IDDM. Furthermore, there were major differences in HLA class II gene profiles according to the age of onset. Patients with onset after 15 yr (n = 290) showed a significantly higher percentage of non-DR3 /non-DR4 genotypes than those with childhood onset (n = 112) and a lower percentage ofDR3 /4 genotypes. These non-DR3 / non-DR4 patients, although presenting clinically as IDDM type 1 patients, showed a lower frequency of islet cell antibodies at diagnosis and a significantly milder initial insulin deficiency. These subjects probably represent a particular subset of IDDM patients in whom frequency increases with age. The data confirm the genetic heterogeneity of IDDM and call for caution in extrapolating to adult patients the genetic concepts derived from childhood IDDM. (J. Clin. Invest. 1992. 90:2242-2250

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