- American Association of Physicians, 2018
- American Society for Clinical Investigation, 2001
- Endocrinology and Metabolism Fellowship, Interinstitute Endocrinology Training Program, NIDDK, NIH, 1986-1989
- Internal Medicine Residency, Montefiore Medical Center, Bronx, NY, 1983-1986
- M.D., Columbia University College of Physicians and Surgeons, 1983
- B.S., Massachusetts Institutes of Technology, 1979
Our ultimate goal is to understand the role that the G protein, Gsα, plays in the development of obesity in children with PHP1a and more generally the role of Gsα and other G proteins in the regulation of energy balance and glucose metabolism. With this insight, we can potentially design therapeutic targets for obesity and diabetes.
Our laboratory studies the genetic regulation, biochemistry, and physiological roles of the heterotrimeric G protein Gs, which is required for hormone-stimulated intracellular cAMP accumulation and other G proteins, with a particular focus on the role of these G proteins in regulation of energy and glucose homeostasis. Using the human genetic model Albright hereditary osteodystrophy (AHO), which is associated with heterozygous inactivating mutations in the Gsα-subunit gene (GNAS), and a mouse model with heterozygous inactivation of Gnas, we have demonstrated that Gsα is imprinted in a tissue-specific manner with the paternal allele poorly expressed in some tissues. This most likely explains why maternal transmission of AHO leads to multihormone resistance and obesity (pseudohypoparathyroidism type 1a, PHP1a) while paternal transmission does not (pseudopseudohypoparathyroidism, PPHP). We have identified an imprint control region for Gsα and have shown that imprinting (methylation) of this region is abnormally imprinted in pseudohypoparathyroidism type 1b, an isolated form of hormone resistance. We showed that maternal Gsα mutations also lead to obesity and insulin-resistant diabetes in mice and that this parent-of-origin effect of Gsα mutations on energy balance and glucose metabolism is due to Gsα imprinting within the central nervous system. We have recently shown that Gsα imprinting in the dorsomedial hypothalamus (DMH) underlies the parent-of-origin metabolic effects of Gnas mutations. In addition we have shown that melanocortins appear to mediate their effects on food intake in the paraventricular nucleus (PVN) via signaling through Gq/11α . We are also conducting detailed metabolic studies in PHP1a and related patients in the Clinical Center’s Metabolic Unit.
Applying our Research
Understanding the mechanisms by which energy balance and glucose metabolism are regulated by the central nervous system is fundamental in helping design future medications for the treatment of obesity and diabetes, two conditions with very significant morbidity and mortality rates and with an ever-increasing prevalence in the general population.
Need for Further Study
We need to understand in which areas of the brain Gsα is affected by genomic imprinting and how Gsα deficiency in these regions leads to such profound metabolic effects.
- The stimulatory G protein Gsα is required in melanocortin 4 receptor-expressing cells for normal energy balance, thermogenesis, and glucose metabolism.
- Podyma B, Sun H, Wilson EA, Carlson B, Pritikin E, Gavrilova O, Weinstein LS, Chen M.
- J Biol Chem (2018 Jul 13) 293:10993-11005. Abstract/Full Text
- Gsα deficiency in the dorsomedial hypothalamus underlies obesity associated with Gsα mutations.
- Chen M, Shrestha YB, Podyma B, Cui Z, Naglieri B, Sun H, Ho T, Wilson EA, Li YQ, Gavrilova O, Weinstein LS.
- J Clin Invest (2017 Feb 1) 127:500-510. Abstract/Full Text
Research in Plain Language
Our lab studies the genetic regulation, chemical processes, and functional role of the Gsα protein, which is required for accumulation of the chemical messenger cyclic adenosine monophosphate (cAMP) inside cells. Our lab studied both a human disease (Albright hereditary osteodystrophy, or AHO) that is associated with mutations in the Gsα-subunit gene and a mouse model with an intentionally inactivated Gsα-subunit gene. Through these studies our lab demonstrated that, in some tissue, the copy of the Gsα-subunit gene inherited from the father is inactive due to a process called genomic imprinting. This explains why maternal inheritance leads to a form of AHO that is associated with obesity and resistance to multiple hormones (pseudohypoparathyroidism type 1a, or PHP1a), while paternal inheritance is not. We are continuing to study these patients in great detail and are developing various genetically engineered mouse models with deletion of the gene in order to understand its role in the development of obesity and diabetes.